fender deluxe vintage modern

[catstrat]

I have a Fender Deluxe vintage modern on my bench. I have voltage to the output tubes plates but not to the 2- 12ax7 tube plates. I checked the power supply and found one bad resistor R69. I replaced that resistor, sure that was the problem, and still no voltage at the 12ax7s. Going by the schematic it looks like any other amp power supply. I have voltage to one side of r69 but not past it. Anyone more familiar with these than me?

[Jazz P Bass]

Seeing that you know what R69 is, you must have a schematic.
Can you post it?

[Enzo]

I'd like to see the drawing also.

SO does your new R69 get REAL HOT? If so, then something is shorting that B+ node to ground. SHorted filter cap, solder bridge, loose hardware touching, whatevr.

[JoeM]

Here it is:

[g1]

So you have no voltage on either side of R68? Then C38 is likely shorted as Enzo mentioned, and R69 should be getting real hot or burning up (or open) again.

[catstrat]

vintage modern

Thanks for the quick response and thanks to Joe m for posting the schematic. I got it off the Fender website. I replaced C 38 earlier and still no voltage. I'm convinced something is shorted along with Enzo, but what. I'm going to lift all filter caps from the circuit and try it then. I've already removed all coupling caps from the circuit thinking maybe one of them was shorted somehow and that didn't change anything. Wouldn't a shorted filter cap also blow a fuse? This is a double sided board and i don't know if this may be a board problem or not, if that's possible. I was bringing up the power with a variac and i did see smoke but shut everything down before i could see the source. The original complaint was no output. I'm going to look closely at the tube sockets and see if one of them is shorted. Thanks everyone and stay tuned for more adventures.

[g1]

Have you measured R69 resistance, is it burnt or open again? Maybe that's what was smoking?

[catstrat]

I just checked r69 again and it's still good. I didn't have a 4.7 k resistor so i used a 5.1 k. Maybe that's it. I lifted all the filter caps from the circuit and brought up the power and i still had no voltage. I also lifted one end of r 69 ,the end that connects to r68, and had voltage. The moment i re connect it , no voltage. I jumped from the lifted end of r69 to the opposite end of r68 and then had voltage the the 12ax7 tube plates. But when i move that jumper to the other end of r68, nothing. R 68 was replaced even the the old one was good. I just don't see anything on the schematic that would cause this or anything on the board. Is it possible to some how have a short within the board itself?

[catstrat]

Alright. Whatever is happening to the voltage is happening at r68. I left the end of r69 disconnected, lifted the other end of r68 totally disconnected from the rest of the circuit and as i jump to the nonlifted end of r68 no voltage. Unhook the jumper and i have voltage. Keeping in mind this is a double sided board so i isolated all circuits from this point on both sides of the board no voltage. I've never seen a resistor short out before. I've cleaned the board. At this point all filter caps are out of the circuit. R69 is lifted on the r68 end and the other end of r68 is also lifted. The tracings on the other side of the board are disconnected as well. R68 is as isolated from the rest of the circuit as i can get it. That's where i'm losing the voltage. I suppose i could just jump everything to make it work but that's a last resort and i don't like doing it. When all else fails, go to lunch!

[g1]

Can you please clarify, with R68 removed, power off. Where is the low resistance to ground, point X or point Y ?

[catstrat]

Thanks everyone for your input. I found the problem. It was board jumper W119 that was touching and arcing a tracing that it was lying on top of. I never would have guessed it. I saw a small burned spot and i lifted the jumper off the tracing and that fixed it. The burned spot was tiny. I set my meter on beep and traced out the tracings until i found that. I'll replace that jumper with a piece of wire and we're good to go, i hope. Thanks again.

[g1]

Kind of silly to run a bare ground jumper across a high voltage trace. Those zero ohm "jumper" resistors would work much better for that, or an insulated wire jumper as you mentioned.
The bare wire jumper shorting to trace sounds kind of "boogie", maybe that's the "modern" part of the vintage modern thing.

[catstrat]

Hi G-one. I guess we all run into problems that confound us from time to time but that problem is something i just don't think to check for. I don't know why they wouldn't have spent a few cents and used a zero ohm jumper. I'm still trying to figure out the modern part from the vintage part.