Musicman RD 100 2100 Cal Chassis

[plexi50]

The amp is drawing too much current under load. It's been 4 months since getting a rewind Power Transformer from Mercury Magnetics. I can read the (2) 1N5353B Zener Diodes. I can not read the other (5) smaller ones. Does 1N4003 look right? I have an actual layout for the 2165 & 2100 RD but as well they don't list the part #.Musicman made so many different amps and schematics i don't trust knowing if im looking at the right ones anymore.

[shooter]

i don't trust knowing if im looking at the right ones anymore.

they should be "good enough" to tell Zener from standard diode, once you figure out they're "regular" diodes you can usually throw in whatever you have based on size n "application".


Diodes typically fail short, then soon burn open, easy enough to test lifting one side.

[sluckey]

Schematic shows five 1N4003.

https://el34world.com/charts/Schematics/files/Musicman/Musicman_2165_rd_2100_rd.pdf

[plexi50]

What voltages should i use for the IN4003 & 1N5353B Diodes? 16 volts?
Also what is that small white diode whatchamacallit?

[sluckey]

What voltages should i use for the IN4003 & 1N5353B Diodes?

What do you mean? You should use whatever voltage the amp supplies. Don't exceed the 200V PIV rating for the 1N4003 diodes. The 1N5353B is a 16V zener. The unregulated voltage applied to the zener must be greater than 16V in order for the zener to act as a regulator.

[shooter]

What do you mean?

2nd that motion 


the bottom side would help to trace the "white" diode, guessing it's D14, a 22v Zener from Steve's schematic

[plexi50]

I have a 32.7 VDC feed to the 370 ohm ceramic resistors before i lifted the board out of the chassis. 
Edit: Disregard this info;

[plexi50]

I re measuered from the yellow CT wire to each orange lead and i have an even 32 VAC on each orange voltage lead.
Sorry im a mess today.  I know accurate info is needed. Just wanted to know the voltages for the diodes.

[sluckey]

Did you get a good answer?

[plexi50]

Did you get a good answer?

Yes. Thanks for the Diode voltage info. The amp was messed with before i got it and the underside of the boards traces where the cap's and 370 r resistors meet were really badly soldered. The traces are less than paper thin to start with. I am just going to rebuild the rectification area and Zener Diodes. I know my PT is good. Thanks much.

[shooter]

The amp is drawing too much current under load.

did you derive that from the "burnt" area?


I ask because a "bad PS" is usually the result of something else, so rebuilding the PS without finding the cause/source will typically result in a bad PS, again.

[plexi50]

The amp is drawing too much current under load.

did you derive that from the "burnt" area?


I ask because a "bad PS" is usually the result of something else, so rebuilding the PS without finding the cause/source will typically result in a bad PS, again.

My limiter bulb dimmed and i flipped it off immediately. After pulling the board today i saw some hackery solder work where the caps and diode traces are. I didn't expect to see what i saw. The voltages of Neg & Positive 16 volts were present. Then it disappeared from one of the caps all together. Anyway i am just going to rebuild the entire burnt area. All diodes Rectifier and Zeners & Caps and 2N6292 tube driver transistors. I checked all the PT voltages earlier today and all is good per the Mercury M spec sheet as far as the power transformer itself.

[sluckey]

Those zeners get hot. When you replace them leave the leads long enough to allow the zeners to stand above the board by about 1/2".

[shooter]

My limiter bulb dimmed and i flipped it off immediately.

my understanding, when it's real bright, things are not good.
anyway;
IF the tubes grid (G1) goes short, that could take out the PS since it provides 22vdc with a Zener for part of it's biasing.

[plexi50]

I would prefer the 12AX7 PI model myself.

[plexi50]

Figured from reading that i would use these transistors instead of the 2N6292.
2N6488 is suppose to be more matched.

[plexi50]

Here is a more detailed and clear pic of an amp i did a few years ago. Thank God for record keeping and documents.
 Hard to get good pics with my crappy phone.