50 watt fire up

Guest · Post by **Guest** » Tue Apr 05, 2005 12:09 pm

Flames1950 wrote:Also check the plate resistors on V3, the phase inverter. I don't think you should have that wide a variance between pin 1 and pin 6. Should only differ by maybe 10% at the most. It's the 82K and 100K resistors in a "V" on the board, pull the V3 tube and you should be able to read the resistor values without removing them from the board.

With V3 pulled, I get a value of 81.2K for the left resistor and 98.7K for the right.

Trem Abuser · Post by **Trem Abuser** » Tue Apr 05, 2005 7:10 pm

Anonymous wrote:
Flames1950 wrote:Also check the plate resistors on V3, the phase inverter. I don't think you should have that wide a variance between pin 1 and pin 6. Should only differ by maybe 10% at the most. It's the 82K and 100K resistors in a "V" on the board, pull the V3 tube and you should be able to read the resistor values without removing them from the board.
With V3 pulled, I get a value of 81.2K for the left resistor and 98.7K for the right.

This was me, neglecting to sign in...

Anyone have any suggestions on what I should do now?

Thanks

Flames1950 · Post by **Flames1950** » Tue Apr 05, 2005 11:55 pm

Something's not right in the B+ voltage line, there should really be only about 200-230VDC on either side of V3. Without pictures I'm not sure if the B+ resistors are wired incorrectly, or if buss wiring is incorrect, or what.
It still blew the fuse even with a 3A slo-blo?
Do you have any way to take pictures that you could e-mail or post?

Billy Batz · Post by **Billy Batz** » Wed Apr 06, 2005 12:00 am

Trem get yourself some good close up pics from the CD or this site and go over each connection one at a time. Ive built a decent amount of amps and I will still always take a break and come back to the amp fresh to look for mistakes before I start it up the first time. Of all the things that can damage an amp impatience is one I cant afford to deal with. Like truckers getting tunnel vision, studio engineers getting listening fatigue and painters getting color blind if your staring in that amp for too long you could be looking at a bluntly obviouse mistake and totally keep going past it. Ive done it. Just take a long break and come back to it tomorrow and go over every component and connection. Unless you can get those pics up!

Trem Abuser · Post by **Trem Abuser** » Wed Apr 06, 2005 12:13 am

Guys, I'll take some pics and post 'em. My digital camera doesn't give the detail of Winnard's, so I'm not sure if you'll be able to see the level of detail you need. But its a place to start.

Also - Flames, no I didn't try with the 3 amp. I bought some 3 amp fuses but I'm going to take the pics and get comments from you guys before I fire it up again because it sounds like something is definitely wrong. I'd like to repair something that is obviously wrong before proceeding.

I'll get as close as I can with the camera and take multiple pics.

Billy Batz · Post by **Billy Batz** » Wed Apr 06, 2005 12:24 am

Just take more smaller close ups as opposed to larger panaramics that can zoom in with detail.

Trem Abuser · Post by **Trem Abuser** » Wed Apr 06, 2005 3:24 am

Here are the pics. Forgive the two Torres .047uf caps in series temporarily taking place of the .022uf cap in the mail.

Trem Abuser · Post by **Trem Abuser** » Wed Apr 06, 2005 3:27 am

The remainder...

I had to resize the pics so tiny as to lose most of the definition in the image.

How do those other guys post such detailed pics?

Flames1950 · Post by **Flames1950** » Wed Apr 06, 2005 8:21 am

Buss wiring looks correct. Can't read the resistor values for sure but they're all present and accounted for otherwise.
Were all the tubes in for those measurements, or just the preamp tubes since you'd had fuse problems?

Trem Abuser · Post by **Trem Abuser** » Wed Apr 06, 2005 1:42 pm

Flames1950 wrote:Buss wiring looks correct. Can't read the resistor values for sure but they're all present and accounted for otherwise.
Were all the tubes in for those measurements, or just the preamp tubes since you'd had fuse problems?

For the measurements given above, just the preamp tubes were in. The fuse doesn't blow with just the preamp tubes in.

Its when I put the EL34s in, turn it on and let it warm up for a minute, then hit the standby switch that the fuse will blow. Fuse will blow approximately 10 seconds after the standby switch is thrown.

Trem Abuser · Post by **Trem Abuser** » Thu Apr 07, 2005 3:09 pm

Billy Batz wrote:Trem get yourself some good close up pics from the CD or this site and go over each connection one at a time. Ive built a decent amount of amps and I will still always take a break and come back to the amp fresh to look for mistakes before I start it up the first time. Of all the things that can damage an amp impatience is one I cant afford to deal with. Like truckers getting tunnel vision, studio engineers getting listening fatigue and painters getting color blind if your staring in that amp for too long you could be looking at a bluntly obviouse mistake and totally keep going past it. Ive done it. Just take a long break and come back to it tomorrow and go over every component and connection. Unless you can get those pics up!

Problem is, even if I were looking directly at a mistake, I do not have the experience to know that it is a mistake. I tried to put everything in as I was supposed to, but there were some things (e.g., the resistor on V2) that I wasn't even aware of.

I've already checked the resistors, I'll check everything against my wiring guide again.

Otherwise, if anyone has any suggestions, please let me know.

Thanks

Flames1950 · Post by **Flames1950** » Thu Apr 07, 2005 3:35 pm

I'd still try the 3 amp fuse, it was standard for 50 watt Marshalls.
This thing was originally the VC30 model, 30 watts? I'd bet if 2 amp was the original value for that original power tranny it just ain't gonna make it here. There shouldn't be a dead short anywhere if the fuse makes it ten seconds.

Trem Abuser · Post by **Trem Abuser** » Thu Apr 07, 2005 3:44 pm

I'll give the 3 amp fuse a try but what about my voltage issues? I'm still concerned my voltages are way off.