Need help with 50 Watt build!!!!!

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 12:38 am

Hey bartak, as a matter of fact, I just got done doing just that, and everything seems to be ok with the wiring. This has me scratching my head.

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 12:41 am

bluze81 wrote:What value is the resistor in front of the diode bias section? should be a 220k I beleive, its hard to tell from the picture.

Its a 150k resistor. Thats what the instructions and the layout calls for.

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 3:31 pm

Something I just found, my impedance selector switch with all the leads connected from the output transformer, seems to conduct all of the wires all of the time. Is this right? If I measure from the center output tab, and I take the other lead of my ohm meter to any of the other leads coming from my output transformer, I measure almost no ohms, no mater what position the switch is in. Even with a cable plugged into the output jack. As a matter of fact, I measure less than 1 ohm from any tap to ground.

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 4:43 pm

As per Georges request, (speaking through Fido) I just took the amp into a dark room to see any arcing and I saw nothing. I still feel the clicking is in the area of the power transformer. I am going crazy trying to find this. I tried to get George on the phone multiple times but he was busy.

Post by **VelvetGeorge** » Mon Nov 26, 2007 5:21 pm

Sorry, I know you're frustrated. It's been a tough Monday for me as well.

If enough current is flowing to make an arc sound, you should be able to see it.
It's not likely, but is possible, that it's your PT. Since this only occurs when the standby is on and the HT fuse is installed.

I did look at your pics and everything appears wired correctly.

This could also be a filter cap. Did you have anything wired incorrectly at first? This could damage them.

It could also be a tube socket. Take a very close look at the terminals and inside the holes.

george

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 6:46 pm

VelvetGeorge wrote:Sorry, I know you're frustrated. It's been a tough Monday for me as well.

If enough current is flowing to make an arc sound, you should be able to see it.
It's not likely, but is possible, that it's your PT. Since this only occurs when the standby is on and the HT fuse is installed.

I did look at your pics and everything appears wired correctly.

This could also be a filter cap. Did you have anything wired incorrectly at first? This could damage them.

It could also be a tube socket. Take a very close look at the terminals and inside the holes.

george

I had it wired correctly from the start. I wish I hadn't because I would have found the problem by now.

I do not see any arcs, it sounds like its coming from the area of the filter caps/transformer/rectifier. I did test the filter caps but they all test at the proper levels.

As far as the sockets, all looks good.

Were do I go from here? How do we proceed?

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 8:18 pm

Here is something I have learned. The popping noise happens when I first turn it on. So I have did a little test. I turned it on, got the popping noise then shut it down for about 1 minute. I checked the filter caps and they were still charged. I turned it on again and no pops. (understand I did not leave it on)

I then shut down, drained the filter caps and turned back on the power bad the pops came back. Does this suggest the filter caps are bad? The funny thing is that they measure ok.

toner · Post by **toner** » Mon Nov 26, 2007 8:46 pm

jctaudiodesigns wrote:...Does this suggest the filter caps are bad?...

I would *guess* that it's a filter cap or the rectifier. There are ways to test the PT, rectifier, caps, etc. but I'll have to let one of the guru's here help you with that. I didn't see any obvious problems in your pics.

jctaudiodesigns · Post by **jctaudiodesigns** » Mon Nov 26, 2007 8:52 pm

I unhooked the rectifier from the PT and it seems ok. I am going to see if George will send me a couple of filter caps.

The funny thing is that the voltages all look good. At the positive terminal on the rectifier I have 455v

jctaudiodesigns · Post by **jctaudiodesigns** » Tue Nov 27, 2007 4:52 pm

Ok, it looks like it is the filter caps. I took my amp in to a friend of mine that works on amps and he seems to think it is one of the 50uF caps. Something inside one of them moves when the standby switch flipped on, and that is what is making the noise. I will let you all know tomorrow when I get the correct part replaced.

jctaudiodesigns · Post by **jctaudiodesigns** » Thu Nov 29, 2007 2:32 pm

Ok........well I replaced the filter cap and the same noise came up. George is trying to help me do a little trouble shooting, but I need some info from you all. It is the CE 50uF can caps that are making the clicking noise. Has anyone had any problems with these caps?

Has anyone ever heard a clicking noise coming from the filter caps cans when you first power up the amp after its been built? If so, does it go away?

George wants me to turn on the amp and keep it on for about 2 minutes to see what happens.

Once again I do thank everyone for your help, it is appreciated.

neikeel · Post by **neikeel** » Thu Nov 29, 2007 4:47 pm

jctaudiodesigns wrote:
Has anyone ever heard a clicking noise coming from the filter caps cans when you first power up am amp after its been built? If so, does it go away?

Nope

jctaudiodesigns wrote:George wants me to turn on the amp and keep it on for about 2 minutes to see what happens.

He da man, so I would do it!

If it goes pop he will still help you out.....I think

bartak · Post by **bartak** » Fri Nov 30, 2007 1:01 am

If it s still making the noise after you replaced the caps I bet its wired wrong or theres a short somewhere. start by tracing the wires back from the cap that is making the noise. I had a bassman that I couldn't fix I went over and over that amp. turns out I had a cold solder joint on one of the power tube sockets, took a week to find it, 30 seconds to fix.

Roe · Post by **Roe** » Fri Nov 30, 2007 5:22 am

jctaudiodesigns wrote:I just lifted the board to see if I could find a place were its arcing, I didn't. By the way, its just not 1 or 2, its a continuous popping sound. It also takes a couple of seconds after I switch standby on before it starts happening.

could it be that your bias is way high?
if so, replacing the 47k bias resistor with a 68k might help

jctaudiodesigns · Post by **jctaudiodesigns** » Fri Nov 30, 2007 8:12 am

Well the trouble shooting begins, last night I disconnected the wires that send power to the choke and the OT and no popping. This morning I think I will put the OT lead back and see what happens.