The Amp Garage

talbany wrote:Anyone know the original FET transistor he used?

2N4416? Someone here must know what HAD was using. All I know is in the #124 pictures the FET looks to be a 2N-something. Vishay/Siliconix have current production 2N4416A in TO72 at about $2.50 ea.

MPM

Nice compact all-in-one PS board! First filter is 4x120uF (?) radials, with two paralleled pairs in series?

MPM

You are probably still going to need to use two in series with balancing resistors to get the voltage rating requirement down. A quick look at the dimensions of 220uF, 300+ volt units shows that they are about 50mm (2") tall and 25mm (1") in diameter, so unless you have an unusually deep chassis you...

The 2x100R are there to create a "virtual" center tap for the heater winding. This is used as a ground reference, which is needed to minimize 60Hz hum in the signal path. If your PT has a center tap on the filament winding, which it does per the schematic posted above, then the 2x100R are not needed...

This schem seems to have the changes: http://www.drtube.com/schematics/marshall/4210.gif Note 4210 combo and 2205 head are same diagram. It shows 1K screen resistors added for US only, and no change to the OT tap used for the NFB. Later versions, i.e. http://www.drtube.com/schematics/marshall/2205pw...

http://ampgarage.com/forum/viewtopic.ph ... back+panel

MPM

What if the bad connection is between the 1-ohm resistor and the socket? If the resistor's ground connection is good, then the current draw is as indicated by your measurement at the resistor lead, 40 mA. You could check the voltage across this resistor directly at its leads to be sure. If this is t...

I wonder if the "shim" is actually as an interface plate between the already drilled chassis and a new transformer with different mounting bolt centers.... I would suspect that to be the case, and it would save HAD from having to drill a vintage, steel (although galvanized, not stainless) Fender ch...

http://www.martinbarre.com/gear.htm

See 1970.

Kinda like this, but not exactly? This is a modern one; I doubt they are compatible with the old standard.

MPM

Described here:

http://www.freewebs.com/valvewizard/bridge.html

MPM

Another option that might be worth a try is the updated Fender trem circuit from the Vibrolux and Vibroverb reissue amps, which can be seen here: http://www.lynx.bc.ca/~jc/tremoloCircuits.html Scroll down to see a link to an except from the schematic. The feedback comes from the follower's cathode, ...

...I'm doing a 100W 6L6 BM so current draw will be in the neighborhood of about 4.5A. Using the calculator and reading off the, "External Layers" column, I get an required trace width of 2.39mm. Should be enough. Also, if I were to fill in the copper traces with solder, I'd think current handling c...

Some good stuff on 1) here:

http://circuitcalculator.com/wordpress/ ... alculator/

Looks like 1-oz x 3mm (0.125 in) width traces should be good for close to 4A on an external surface. Maintain that as a minimum and I think it should be fine, no?

MPM

Nice work! A couple of questions, if you don't mind: How much of the circuit is modeled? Sounds like you have at least the whole clean section since you say no NFB is included. It would be nice to establish a reference case for the standard pre-amp circuit. What are the setting of the switches (Brig...