What seems to be ages ago, we ran out of the Atari CO20561 / CO20192 Fire button PCB's. Well after hundreds and hundreds of World Wide requests, the Atari CX24/CX22 Fire button PCB's are back in good supply. CO20561/CO20192 Fire button PCB's $2.50 each.

Shown above the CX24 Fire button PCB's, the Atari CX24 Joystick X-Y replacement PCB board CB101239 $2.50 each.

Atari CX40 Joystick Users! New Improved/Upgraded Atari Replacement Inner Joystick Handle!

Are you one of those Die Hard Atari users who still Like/Love/Use the first Atari Joystick ever made, the Atari CX40? Shipped and Used with all of the Early Atari Systems made (except the CX5200 Model) and still a Classic Bench Mark Joystick today, some 23 years latter!

Over the years Atari made only 1 Major Change to the Atari CX40 Joystick design. The early Pre 1980 version CX40 Atari Joysticks had a flexible white or black plastic plate over the X / Y PCB board with 4 heavy duty Springs that attached to the Joystick Handle (a True Atari Collector item now a days) on the inside of the Joystick. This version Atari CX40 Joystick was soon replaced with the current version with only the Plastic handle and X / Y PCB board. Over the years Atari Engineering made many minor, almost hidden improvements to the CX40 joystick over the Millions and Millions that were produced.

One of the Best and Last improvements Atari Engineering made to the CX40 Joystick was an Improved Replacement CX40 Inner Handle (CX40 Handle bottom on the Right). As you can see the outer ring with the plastic contact points was Beefed up (Thickened) and Stress Relieving slots with Stress Relieving round edges were designed in, where the Older version CX40 Handles always failed

New Improved/Upgraded Atari CX40 Handle CO12116U $3.95 ea

Special Buy! Limited Supply

The Pro-Stick Joystick is like a standard CX40 Joystick but with a Red Base/Black Top, Red Joystick boot, Left or Right side dual Red Fire buttons on the base (for Left or Right handed People), Molded Plastic Handle Grip with Top Fire button too and Joystick cable comes out of the center bottom of the Pro-Stick!

Best Electronics Latest and Hottest 33.33X Upgrade to an Atari 23+ Year old Atari CX40 Joystick Internal Design!

Best recently sold out of the Stock Atari made CX40 Joystick internal Printed Circuit Boards (PCB) we acquired from the Local Atari Sunnyvale Warehouses when we bought out the Atari parts division. Tiger Tach Rebuild
Sept 27, 2000
Update: Nov 15, 2002

Motivation
The Tiger tachometer is a source of frustration for many Tiger owners. It may work, or not, or intermittently, and when it does, it is sensitive to temperature and other weather variables, and on the whole, it is not a gauge one would want to use to monitor critical engine functions. Others have reverse-engineered the Smiths design (see Mark Olson's description) to determine replacement components and (see the STOA Tech Tip) modified the tach to work with electronic ignition amplifiers, but the basic design deficiencies still remain if the circuit is kept as it was designed about 45 years ago.
The existing design uses a simple transformer to detect the current pulse that occurs every time the coil fires. The resulting signal is converted to a constant-width, constant-voltage pulse using a two-transistor circuit. The constant-width pulses then drive the meter movement; the closer together the pulses, the higher is the average voltage, and the greater the meter movement deflection. The downside of this very simple circuit lies mostly in the component choices and the fact that there is little compensation for component aging or temperature. Since I was planning to install an MSD ignition amplifier, I needed to modify the tach anyway, and I decided I might as well update the internals to at least the '70s. Interestingly enough, that didn't really simplify the internals of the tach...

The power supply works from the Tiger's 12V electrical system and provides a filtered 8 volts to the rest of the tach. The resistor and Transzorb on the input are intended to protect the regulator from voltage transients that exceed the regulator's capabilities. The calibration oscillator provides a 30% duty cycle output signal at a fixed frequency that corresponds to approximately 3500 RPM. The idea is that I will measure the frequency (or period) of this oscillator using the scope, determine what RPM that corresponds to, then tweak the tach driver adjustment until the tach reads the correct RPM. The ignition input basically consists of some filtering and protection so that the 555's trigger input is protected from the ignition circuit. The tach driver uses an adjustable resistor that gives a fairly wide adjustment range of the output pulse width to allow for unit to unit variability as well as tuning for 4, 6, or 8 cylinder engines. The 100 ohm resistor in series with the meter movement, combined with the pulse width set by the resistors and capacitor, together determine the meter calibration. I wanted the pulse duty cycle to be about 50% at 6000 RPM, so I juggled the output resistor and the 3.3K resistor value until I got there.

If you compare this to the Smiths design, you'll see that things definitely didn't get simpler...

Construction
I started by disassembling the tach (follow Mark Olson's procedure!) but I found that in order to remove the PCB, I had to remove the needle and face. I put a small stack of business cards between the face and the needle center, under one side of the needle shaft, then put one card on the other side, and used a screwdriver to wedge the needle off of the shaft. This took more force than I liked, but I didn't bend the shaft. Then I removed the face plate. One thing that was interesting is that the opening for the panel light is partially obscured by the printed circuit board. This tach had a large crack in the timing capacitor (dark red cylinder on the upper left).
Another view of the tach electronics, showing the meter movement. The two spiral springs transfer the coil current from the stationary contacts at the top to the coil which is mounted on the rotating shaft.

I measured the mounting hole locations and cutouts necessary to clear the meter movement, and made up a drawing on the computer. I measured the components that I was going to fit and spent a while juggling placements and wire routing options. After I got to a reasonable answer I printed the result and then cut out the pattern on a piece of prototyping board (one-sided copperclad and tin-plated). Since I don't like drilling lots of small holes I decided to use a poor-man's surface mount method, where you basically clip the leads off of anything that you mount to the board. The traces were cut using an X-acto knife, after marking all the component lead locations. Company List
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For this prototype I used primarily leaded parts (with the leads cut off as required) but a few surface mount parts did find their way onto the board. Going to full surface mount would reduce the clutter quite a bit but some surface mount parts are a little more fragile than the leaded components and I didn't want to be chasing a cracked resistor at some inopportune time. The aerial wiring is part of the calibration connection, which I removed once I'd reassembled everything and tweaked the calibration adjustment.

I needed to make some adjustments to the mounting hole locations but things went together pretty well. Note that the meter movement is a balanced assembly and until the needle is back on the shaft, the shaft position will be dependent on how you've got things tilted. This is especially important to keep in mind when you're reassembling the needle on the shaft. I left the current sensing transformer on the backplate PCB, and just soldered its wires (just visible on the lower right) to the main PCB so they wouldn't get in the way.

I drilled a 1/4" hole for a grommet to lead the tach input wire out. I did not make the calibration controls externally accessible but I will probably add that later.

What Next?
Even having made these changes I expect this tach to be accurate to no more than 100 RPM or so, based on the fact that repeated connections of the calibration signal would cause the needle to stop up to 100 RPM away from the calibration point (which was 3191 RPM in my case). The big difference is that I expect that the tach will be accurate at least over the normal temperature range in which I drive my Tiger, and that this accuracy will still be there five or ten years from now. The tach doesn't have very fast response, mainly due to the inertia of the meter movement, but this could be improved somewhat (at least on the acceleration side) by characterizing the mechanical inertia and the electrical inductance precisely, and then determining a more optimal control solution, so that response speed is maximized while minimizing overshoot, but this is not necessary for any but the most highly tuned engines, and in that case you'd be better off using a real tach anyway...

Equipment
I already had a 7000 RPM tach from a series V alpine, which is internally identical to the Tiger tach. The Smiths meter movement has a mechanical stop at each end of the scale, which prevents one from using a stock Tiger tach on any high-performance engine that will exceed the tach's 5500 RPM capability. The Alpine tach is an easy way to get a 'high-performance' instrument that still matches the rest of the Tiger dash trim, as long as it is recalibrated for the V8 ignition. My calibration instrument was an oscilloscope (if you must know, a Tek 5101 analog flood-gun storage scope). Basic electronics tools are absolutely essential, as is some experience with PCB assembly and rework.

Design
The spark for this design came from a discussion I had over dinner with Gary Winblad, at SUNI III. He suggested using a 555 timer circuit to replace the tach guts. I decided to do that, and at the same time, provide an internal calibration source for the tach so that I wouldn't have to lug the scope around, or so that you could build the circuit board, determine the calibration value for the reference, and then anyone else could bolt that circuit board into their tach and do the calibration with no need for test equipment on their part. The other parts required were a power supply, and an input circuit to condition the pulses from the ignition amplifier or coil. I haven't yet designed an input circuit for the current-detector transformer that the stock tach used. The schematic is shown below:

Best has been selling this basic replacement Atari CX40 Internal PCB board for some 21+ years now. The basic design and manufacturing techniques used to make this replacement Atari CX40 internal PCB board are based on an Atari original 1979 (contact wires on 2 sides of the PCB board) and the latter 1981 Atari Engineering design (contact wires on the right side) and early PCB board manufacturing techniques of the same era, which have not changed much over all of the different designs and production runs of this CX40 Internal part. The basic Idea, was to make the next production run of this Atari CX40 PCB board a little cheaper each time it was made.

1979 Atari Original Design 1981 Atari Redesign

Over the years Atari used several Styles / Shapes of this Internal Atari CX40 PCB board (all of then completely interchangeable on the Second generation Atari CX40 Joystick) with many different styles of metal Dome contact internal switches and different types of plating on the internal Circuit Traces from Tin, Nickel to Copper.

Because of Best Electronics 23+ year experience in the Atari business, we are Very aware of all of the different Failure modes of all of the Atari CX40 Internal Joystick parts. The last major Upgrade Atari Engineering did to the CX40 Joystick was the Upgraded / Beefed up Design Internal white plastic handle. Click on the Best CX40 Button below to read up on this Upgraded Atari CX40 Handle. This Upgraded Atari CX40 Handle helped fix one of the Known problems with the life expectancy of Atari CX40 Joysticks. But unfortunately the Atari CX40 Internal PCB board 1979/1981 basic design was never upgraded by Atari Engineering until Now!

"Your company name is truly fitting. I installed a set of your gold contact circuit boards in a pair of CX40 joysticks. They're fantastic! These boards are the best thing to happen to the 2600 since the creation of the console itself! I couldn't be happier with my joysticks now. They're better than new! Thanks for making such a great product!" Kevin M. of OH

All of the years Best has been in the Atari parts business, we have seen at least 6 to 8 different Atari CX40 PCB boards made by different Atari parts Manufactures / Suppliers. All of them are known to have different Failure rates and type of Failures.

Just some of the different type of CX40 Internal PCB board failures we have seen over the last 23 years:

Dome Contacts flipping inside out.

Dome Contact fatigue failure (flatting out).

Dome Contact no longer making proper contact with mating PCB circuit trace.

Dome Contacts Shifting their location on the PCB boards.

Failure of the clear plastic cover tape over the dome contacts.

Cracking / Breaking of the Phenolic base material the CX40 PCBs are made of.

Corrosion on the Copper and Tin Traces under the Dome Contacts.

Foreign Materials under the Dome Contacts (failing clear tape cover).

Moisture under the Dome Contacts (failing clear tape cover).

One or more of these problems on an Atari CX40 Joystick Internal PCB board would mean a failure of an Atari CX40 Joystick prematurely.

Using the same Engineering attitude (make a State of the Art Upgraded Replacement part using State of the Art Materials, State of the Art Manufacturing Techniques and New Tooling) that Best Electronics used on the 5200 Gold CX52 Joystick Upgrade Project, we knew we could produce an Improved / Upgraded Atari CX40 Internal PCB board. Every 5200 owner who Now owns one of these Best Exclusive Lifetime Gold Upgraded Joysticks will tell you, that the Best CX52 Gold Joystick upgrade Cured the 20+ year problems that have always existed with the Old Atari made CX52 Joysticks.

As part of our initial research for this Best CX40 PCB upgrade board project, we contacted one of our Oldest Quality Atari parts suppliers we have been using for 15+ years now and had them run some Life cycle Tests on the Old Design (1981) Atari CX40 Internal PCB board. In the Industry it is know as Mean Time Between Failures (MTF) or basically how many cycles a part would run before it failed.

The new PCBs are astonishing. I have no regrets about upgrading to this new PCB. It is superior in every way over the original. Jeff P. of VA

We had our Manufacture run a MTF Test on what Best Electronics considered one of the better 1981 designs of Atari PCB boards (pictured above) we have sold over the years. Their Tests showed that this Atari 1981 designed New replacement CX40 PCB board, only ran about 150,000 cycles before it Failed. The original Atari 1981 Engineering Specification on this version Atari CX40 PCB board, called for minimum MTF of 1,000,000 cycles.

The Best New State of the Art New Upgraded replacement Atari CX40 PCB boards, have New Upgraded Glass Epoxy Stronger PCB board base Material, New 100% Hard Gold Plated Circuit Traces with approximately 55% larger Gold trace contact surface area under the dome contact,

Close up view of the CX40 PCB board Under the CX40 dome Contact fire button area

Atari CX40 Fire button Trace New Best CX40 Fire button Trace

larger Internal contact surface area on inside of the Gold Plated 4 leg Dome Contacts (4 Leg Dome contacts are Hard Gold Plated on the inside of the dome contact surface area and Stainless Steel base material on the Outside surface) and State of the Art 3M Scotch Brand Hi Performance Clear Polyester film covering with escape air channels around the dome contacts. Our Manufacture conservatively Rates this New State of the Art CX40 Upgraded Best replacement PCB board at 5,000,000 cycles MTF or approximately a 33.33X increase in real world MTF cycles compared to the above 1981 Atari designed CX40 PCB board that was tested.

New Best Gold CX40 PCB board!

Essentially the New Best Gold CX40 PCB board should be a lifetime version CX40 Joystick PCB board. The Upgraded Atari CX40 internal handle will fail before this New 2005 Designed State of the Art Best CX40 Gold PCB board.

Over the years Atari used many different style of Dome contacts on the old CX40 PCB boards. Round with top dimple, Round without top dimple, ? round / D shape, several different styles of 3 Leg Round Dome Contacts with different top dimples sizes, were just some of the different types of Dome contacts used. Many of these Dome contacts had a Tactical Feed back (click sound) when they were activated and some were completely Silent when you used the Atari CX40 Fire button and Joystick handle functions.

Our research on different dome contacts found that the ones with a top dimple were quieter when used inside an Atari CX40 Joystick, but they actually had less internal contact surface between the inside of the dome contact (because of the small square surface area of the extended small dimple) and small circuit trace under the dome contact,

Close up, underside view of Dome Contacts

Old Atari 3 leg Dome contact Best larger Gold plated 4 leg contact

which would mean they would fail sooner. Best choose to go with a larger Smooth 4 leg Gold Plated Dome contact to Maximize the contact surface between the inside of the dome contact and the Newly increased larger surface area on the mating Gold plated PCB trace under the dome contact.

The New State of the Art Best Upgraded CX40 Gold PCB with Gold Plated 4 leg dome contacts, have a Good Tactical feed back feel (Louder click compared to the original Atari CX40 joystick PCBs) on the Atari CX40 Fire button and Very light Tactical feed back on the Atari CX40 handle action.

The Original 1981 Atari Engineering Specification called for a Maximum (Dome / Trace) contact resistance of 150 Ohms or less on the CX40 PCB boards. The New Best Gold CX40 PCB boards have contact resistance less than 2 Ohms!

Joe C. of AZ "The upgraded Cx-40 PCBs are excellent. Iˉ?0ll begin reordering these in larger quantities"

Another built in Upgrade on the New Best CX40 Gold PCB board, is the internal Atari CX40 Wiring sequence Color Codes are now etched into each connecting tab. So you will never have to look up the CX40 Color Code wiring sequence and never make a mistake and wire up a rebuilt Atari CX40 Joystick wrong.

Because of the High Cost of the New PCB Tooling, New State of the Art Upgraded Materials and Cost for the first 2005 production run of these New State of the Art Gold Atari CX40 PCB boards, Best Electronics will require the following Minimum orders for these New Atari Gold CX40 internal PCB boards and upgraded CX40 Rebuild kits.

Best Upgraded Gold CX40 Internal PCB CO121110G $6.50 each (Minimum 3 Qty per order)

Atari CX40 Rebuild Kit with Atari Upgraded CX40 Handle and Best Gold CX40 PCB Board CB101211UG $9.95 each (Minimum 2 Kits per order)

Also See Atari CX40 Joysticks upgraded with the New Best CX40 Internal Upgrade!

Add Best Electronics All Atari Web site to your Internet Explorer Favorites folder.
Copyright ? 2002 Best Electronics
Best Electronics in the Atari business since February 1, 1984.

This page Last modified: February 14, 2007
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WATERS REBUILDS AND EXCHANGES
PART NUMBER
DESCRIPTION
REFERENCE
PRICE

DL05162RA1
Waters Rebuilt 710 WISP Injector Assembly
O5162
$300.00

DL34485RA1
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34485
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DL77319RA1
Waters Rebuilt 710, 712 WISP High Pressure Valve Assembly
77319
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DL73260RA1
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73260
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DL98628RA1
Waters Rebuilt 710, 712, 712N WISP R.A.D. Assembly
98628
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Waters Rebuilt 710, 712, 712N WISP Carriage Drive Assembly
77304
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DL73180RA1
Waters Rebuilt 710, 712, 712N WISP Carriage ReaderAssembly
73180
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DL72184RA1
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72184
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DL73183RA1
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73183
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DL72899RA1
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72899
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DL73921RA1
Waters Rebuilt 710 WISP Fluid Pack Assembly
73921
$1,500.00

DL34486RA1
Waters Rebuilt 712 WISP Fluid PAck Assembly
34486
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DL34482RA1
Waters Rebuilt 712N WISP Fluid Pack Assembly
34482
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DL77202RA1
Waters Rebuilt 712 WISP Seal Pack Assembly
77202
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DL34490RA1
Waters Rebuilt 712N WISP Seal Pack Assembly
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45559
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97187
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DL34430RA1
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34430
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DL60042RA1
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60042
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DL60058RA1
Waters Rebuilt Pump Head Assembly
60058
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DL72590RA1
Waters 710, 712, 712N Reconditioned Interconnect PCB
72590
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DL72570RA1
Waters 710, 712, 712N Reconditioned I / O PCB
72570
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DL72693RA1
Waters 710, 712, 712N Reconditioned Combus PCB
72693
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DL72800RA1
Waters 710, 712, 712N Reconditioned CPU PCB
72800
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DL72230RA1
Waters 710, 712, 712N Reconditioned Power Supply Assembly
72230
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DL26387RA1
Waters M45 Reconditioned Power Supply Assembly
26387
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DL26388RA1
Waters M45 Reconditioned Pump Driver PCB
26388
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DL21008RA1
Waters 501, 510 Reconditioned Pump Driver PCB
21008
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DL25400RA1
Waters 6KA Reconditioned Pump Driver PCB
25400
$250.00

DL00717RA1
Waters 715, 717 Reconditioned Power Supply Assembly
$400.00

VARIAN REBUILDS & EXCHANGES
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DL00024RA2
Varian 3700 Rebuilt Electronics Module (Must Specify R/O, ALTP, Electrometer
$1,250.00

DL0200187100A2
Varian 3000, 4600, 6000 TCD Detector Rebuild
02-001871-00
$1,000.00

DL0001RA2
Varian 3000 Series Printed Circuit Board Exchange
$995.00

DL00002RA2
Varian Vista Series Printed Circuit Board Exchange
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DL00003RA2
Varian 5000 Series Printed Circuit Board Exchange
$625.00

DL00004RA2
Varian 5500 Series Circuit Board Exchange
$795.00

INSTRUMENT REFURBISHMENT & OVERHAULS
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REFERENCE
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DL710712A1
Waters 710, 712, 712N WISP Overhaul
$2,400.00

DL00018A1
Waters M45, 501, 510, 590, 6KA Pump Overhaul
$1,000.00

DL00600A1
Waters 600 Pump Overhaul
$895.00

DL003700A2
Varian 3700 Gas Chromatograph Overhaul
$2,200.00

DL005000A2
Varian 5000 Series LC Overhaul
$1,795.00

DL006000A2
Varian Vista Series Gas Chromatograph OverhaulHome
Introduction
Rebuild Discussions
Visiting Mikey
Design Details
More Details
Comparing The Amps
The Build - Part 1
Bias Test Points
The Build - Part 2
The Build - Part 3
The Build - Part 4
Mercury Magnetics
Another Visit to Mikey
Playing The Amp
Contact Information
Guestbook
Comments
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What's New

A matched pair of NOS, NIB Visseaux 6V6 power tubes from Lord Valve

In the last section I talked about 6V6 tubes for power amplification. I thought youd enjoy seeing this photo of two 6V6 tubes; the type of power tube used in Deluxe Reverb amps. These particular 6V6's are some of the best ones ever manufactured. They were made in 1951 for the French military. NOS means they were sold as New Old Stock (never used).

They are also NIB, which means they are essentially New In the Box. These are beautiful sounding tubes that compare favorably with the famous RCA blackplate 6V6s. For new tube manufacturers of 6V6 tubes, I like Electro-Harmonix and JJ Electronic. I usually purchase my tubes from Lord Valve of NBS Electronics in Denver, Colorado (USA). You can get on his detailed tube mailing list for the latest information and pricing:

CTS pot (left), Switchcraft jacks, Alpha pot (right)

NBS Electronics

One of the things I dont like having to do is to take my amp to a tech for biasing when changing power tubes. The DRRI has a bias adjustment on the bottom of the chassis, which is a good quality CTS 10K bias pot so Mikey reuses this part in the rebuild. As I mentioned, Mikey is adding an optional mod to my amp so that I can bias it myself without opening up the amp and exposing myself to lethal charges or having to buy an external bias probe. Mikey solves this by adding three test points on the back of the chassis so I can set my own bias with a voltmeter using the cathode resistor method.

The way this works is a 1-ohm 1% resistor is placed between ground and pin 8 on the power tubes. When you plug a voltmeter into the test jacks, itll measure the voltage drop across the resistor. When I pick up my amp from Mikey, well play with the bias on the tubes to find the spot that sounds best for me and is within the operating parameters of the 6V6 tubes. When it is time to replace my power tubes, Ill buy a matched pair and then re-bias the amp to these same settings. This is really a nice way to make the amp user-friendly.

Mikey and I had been knee-deep-in-the-hoopla for 3.5 hours and we decided it was time for a break. We went to the kitchen and got a couple of Cokes, ice and glasses and sat outside to relax a bit. I continued to ask Mikey about the technical details of the rebuild and about tube amp electronics.

Mikey told of his time in the military and his assignment in Alaska where he played concerts with his band. At one big concert, he played to a huge crowd sharing the bill with Little Feat, Tower of Power, W.P. Brennan from Australia and 14 other local bands. It was like a mini Woodstock and it sure sounds like it was a lot of fun. After this brief respite, we returned to the shop and picked up where wed left off.

Next up was a discussion of the typical negative feedback loop (NFB) used in the Deluxe Reverb and the tweaking Mikey has done to get the best response out of it. I learned that a global NFB loop is created by taking the signal from the output transformer at the positive terminal of the speaker jack and sending it back through a resistor to the phase inverter, which is at point earlier in the circuit before the power tubes. It is called negative feedback because this output signal is 180 degrees out of phase with the input signal.

Mikey experimented for a long time to find just the right resistor so that it wouldnt mess with the clean sounds except making them a bit fatter with more harmonics. It also helps the tone when the amp is pushed hard, giving the amp more gain and girth. I was to experience this later when we started trying out the amps. Heres what Mikey had to say about his modification to the NFB loop.

This acts like a fixed Presence/Resonance control. Presence usually only allows the higher frequencies to pass through without going through the NFB circuit, and Resonance usually lets the lower frequencies through without going through NFB. The resistor mod that I'm using works with all of the frequencies, it doesn't only pass either high or low frequencies. It restricts the amount of signal that goes through the NFB circuit so that it leaves a portion of all of the frequencies to be reproduced naturally, without NFB. NFB reduces distortion and makes for a cleaner tone. Since a portion of the tones aren't going through the NFB circuit, they're reproduced fully, with more harmonics and Phatness!

Regarding the phase inverter (PI), Mikey does some mods to this circuit too. This includes putting in a very high-quality coupling cap leading to the PI because all of the signal from the entire preamp section, reverb and tremolo pass through it on the way to the phase inverter. The PI caps themselves are also of high-quality. Heres what Mikey has to say about his changes to the phase inverter circuit.

The PI caps were modified to prevent the "farting" when playing at high volume. The PI coupling cap was actually raised a bit, to compensate a little for the PI cap change, and to let some more midrange/fullness through from the preamp circuit to the PI. My philosophy is that it's better to make several smaller changes/mods throughout the entire circuit than to just make one large/huge change and throw everything else off. Where I make one change, I usually try to make another small compensating change somewhere else in the circuit.

Another enhancement Mikey makes from the stock DRRI is that he removes the Fender pots and jacks attached to the PCB and replaces them with new pots and jacks; wiring them directly to the appropriate parts of the circuit. He uses CTS and Alpha pots and Switchcraft jacks.

The Alpha pots fit the existing holes but in order to use CTS pots, the holes must be enlarged. To do this, Mikey uses UniBits (step drill bits). His design calls for using shoulder washers to insulate the input jacks from the chassis to help keep the amp quiet. The input jack holes have to be enlarged to 1/2to accommodate the insulating shoulder washers.

Mikey puts the Normal channel in phase with the Vibrato channel. If this isnt done and you try to play the amp when using both channels simultaneously, the sound is really puny since they are out of phase. This mod also has the advantage of routing the Normal channel through the tremolo and reverb circuits, which isnt normally available on a Deluxe Reverb. The Normal channel is also modified to give Marshallesque tone and gain. He explained his goal is to add an extra midrange emphasis and allow the circuit to overdrive sooner.

During our conversation, I became curious about the use of different types of capacitors and how they are used to modify tone. Mikey explained to me how a capacitor works and showed me examples of film and foil caps and metallized caps. He had a couple of them disassembled and he used them to help me understand how caps are constructed.

I now know that film and foil caps use two strips of film and two strips of foil, with a set of film and foil strips creating one Metallized caps have two strips, each with an aluminum conductor atomized and vapor deposited on dielectric film. In both cases, the two layers are rolled up together so there is an anode conductor and a cathode conductor separated by a layer of film.

Two different methods of construction are evident in these two types of capacitors

Film and foil caps are much bigger than metallized caps. You can see this in the picture above. Both caps have the same .03uF/600V rating, but the polypropylene and foil cap is much larger/rounder than the metallized polypropylene cap on the right. On the left, the metal foil is less shiny and crinkled looking when unraveled. On the right, the metal looks very shiny and smooth since the metal was sprayed directly on to the dielectric (the polypropylene film).

The way a capacitor works is when power is applied from the positive and negative wires from the power supply, it becomes charged (one of the layers becomes positive and the other negative). Even with the power supply disconnected, the capacitor will continue to hold a charge. How much of a charge it can hold is measured in Farads (F). Another measure is the voltage rating, which tells you how much DC current the capacitor will block. In the above photo, the capacitors are rated at .03 microfarads and 600 volts.

While capacitors will block DC current, they will allow AC current to through. In actuality, capacitors cycle through charges and discharges somewhat like a very fast, rechargeable battery, which appears to be a flow of AC current. Interestingly, this cycling happens to let high frequencies pass through more easily than low frequencies. This means that capacitors can be used to shape tone in addition to passing an AC signal from one circuit to another without letting any DC current to get through.

There are many types of materials used for cap construction but polypropylene and polyester (foil or metallized) are the most common. Other examples of capacitor construction are paper/oil, polystyrene, polycarbonate, mica and ceramic. Mikey had this to offer on his choice of capacitors (note the preparation he did for my visit based on our voice and email correspondence).

I generally prefer polyester caps overall as they give off a "warmer" tone/more midrange, which is especially nice in a bright Fender circuit. But I changed the caps in my amp for your demo and used polypropylene Orange Drops for the PI caps and PI coupling cap. I also used them in the normal channel tone stack and a couple of other places since you like a brighter tone. Polypropylene gives off more highs and more lows to my ears. Those were polypropylene/foil caps, 716P's. Polyester, either metallized or foil, tends to give more mids and upper mids.

Mikey explained a technique he will to use for the building of my amp. He calls it Cap Stacking, which is the use of a combination of caps of different types wired together to get the tone and grit characteristics to best fit his redesigned circuit and my particular tone preferences. I really enjoyed this part of the discussion and learned a lot I didnt know about caps. As you can see, there a lot of attention to detail that goes into the design of Mikeys amps.

There is an option Mikey uses that I did not select. On his amp, Mikey added a pot on the back of the chassis to the Normal channel to have variable control of the midrange EQ. This lets you dial-in just the right amount of mids for your particular guitar and for the sound you are going for. Mikey installed this extra pot in place of the extension speaker jack. Since I sometimes like to use a Celestion Alnico Blue extension speaker, Mikey said that when we try out his amp, I can find the sweet spot of the mids on his amp that best suits my taste preference. Hell measure the resistance of the pot at that setting and just build it into the circuit of the Normal channel, leaving the extension speaker jack available.

The tremolo circuit is different from the stock DRRI circuit. His tremolo circuit uses the bias to pulsate the power tubes to generate a smooth tremolo effect rather than the on/off type found in the DRRI, which uses an optoisolator. He also slows down the tremolo circuit and raises the intensity a bit to get the most pleasing sound.

The reverb circuit is also significantly different from stock in several ways. The DRRI uses lower quality, PCB housed RCA jacks, which Mikey replaces with heavy-duty RCA female jacks affixed directly to the chassis. To do this, another hole has to be drilled in the chassis but the quality is worth it. I chose the option to use a high-quality Mercury reverb transformer. As anyone that uses a Fender amp with reverb knows, if you turn the reverb knob up past 2, it gets pretty boingy and surf-like. This is because of the use of a linear pot on the stock DRRI. Mikey uses an audio pot for this application so the user can have finer control of the reverb by allowing more incremental changes. Heres Mikeys explanation to me of the differences between linear and audio pots.

Linear pots are the same price as audio pots. It's in the way that the pots function that makes the difference. The resistance of a linear pot is, well, linear! It's in equal increments. For example, if you have a 100K linear pot, and you turn the knob to the halfway point, the resistance will be 50K. An audio pot functions differently, but it functions closer to the way that our ears hear. For the same 100K pot, the halfway point may only represent about 20% of the total resistance, or about 20K.

As the knob rotates, the resistance goes up more, then finally arrives at the same 100K total resistance value. But, it's that first half of the audio pot that gives us finer control, to get those "in-between" values, and again, human ears "hear" in audio fashion, not linear. That's one of the reasons that on the Fender reverbs that use linear pots, it sounds like it's "all on" even when the knob is only on 2 or 3. An audio pot would be halfway up approximately to get that same level.
On some of the less expensive amps, some makers use linear pots on their volume controls so the customer thinks the amp is "loud". Imagine being in a store and trying out an amp, turning the volume up to 2 and blasting out the store. The customer would think that this was one loud amp, but the linear pot makes the ears think that the amp is loud when it's just giving more volume upfront due to the nature of the linear pot. With an audio pot, the volume control may have to be up around halfway to get the same perceived volume.

We finally finished going through the various parts of the amp and all of my questions had been answered. At this point, Mikey and I had been talking for about 5.5 hours and we hadnt played a note yet. It was time to change that!