A little sr-45 troubleshooting help.

[jrebman]

Sometime back I replaced the coupling caps in my sr-45s with v-cap CuTF caps. No problem -- both amps worked fibe for a while and then one began cutting in and out. I traced this to the bottom hole of the terminal strip next to the grid chokes (next to the SR board) For some reason the grid stopper wire was able to move back and forth in the lower hole of te terminal strip. I then soldered it but was never happy with the solder job and eventually after enough fiddling around the grid resistor lead broke too short to reuse. I replaced this resistor and still no sound. I've been all over all te connections from the coupling cap to the grid of the 45 and I see nothing amiss.

Today I loosened the grid choke to look around. All seems fine but could somebody please tell me what the circuit from the 6cm7 to the grid of the 45 looks like? I don't know what pin it is, should it be directly connected to the one side of the coupling cap or is there a resistor supposed to be there (below the coupling cap. On the other end it all looks fine -- coupling cap to junction of grid choke and grid stopper on the 45 and the other side of the grid choke grounded.

At this point I'm beginning to suspect a bad pin in the 6cm7 socket, but I don't know whch one and I'm having problems tracing it out.

Thanks,

Jim

 

[jrebman]

Ok, a little more poking around and I found a loose wire frrom the SR board to the 9 pin socket -- problem is that I can't tell where it came from.

The wire is the one in the far right, lower corner (opposite the 0.1 cap) and apparently right in the corner of the board.

I have no schematic or manual so I'm dependent on somebody who may have built one of these and can tell me where this wire should go -- I think this could be the problem as the part of the circuit I worked on rings out perfectly.

FYI, when the amp is on there is a very gentle hum through the speaker (the same as the other amp) but it appears that no signal is getting through. BTW I never touched this part of the circuit and man, is it tight in there.

-- Jim
b

 

[debk]

Jim

Is this the wire coming from the K pad on the board near the LM431.  If so it goes to the pin 9 of the tube.

Deb

 

[jrebman]

Deb,

Thanks for the help but I have the old original board and I thought you have a newer, modified SS board?

Aside from that I can't read the pads. What an amazingly difficult time just putting the thing back together. I think I'm going to send this one in as without a schematic, resistance and voltage checkout values, I'm more than shooting in the dark here and as I said, it's very tight under there, even with the board freed from the bolts on the standoffs.

-- Jim

 

[debk]

I have the boards from the original SR45 upgrade kit.

Deb