Seeburg USC-2 w/ TSA 10 code B amp.

Steve, if wiring on the cart socket is at fault here (often is) here is a shot of the colors involved:
http://s1192.photobucket.com/user/Rob-N ... sort=2&o=3

Closest to the camera are black and red.

This problem has come up before in this, and other forums. It was never a great design and over time the plastic clip deteriorates and breaks. I still have some of those arm assemblies with a narrow band of tape that i applied back when I was using them in the 80's.

Rob

Hi Rob,
Thanks for that info. At least the problem has been found, when I removed the cart. socket, I found one of the wires had come off the pin so it must have been touching the other wires and the pin at times making all the noise and causing no reading on the meter.
Will work on it again this week sometime, need a break right now! I'll update when I get back to it.

Thanks again for your help,
Steve K.

Hi Everyone,
Checked the phono cart. and socket, had to re-solder one wire back. Still have "noise" and little volume from a record. Checked the RCA connectors on the AMP, cleaned and made sure they were tight with the RCA plug pins. I noticed on the Orange mech. connector on top of the amp, there are only 3 wires running from the cable to the connector, on the amp side socket (J5103), there are 4 pins, is there a wire missing? I checked the schematic and there are 4 connections in the amp, I'm missing the wire attached to pin #6, the schematic says it's the AVC disable? Does this have anything to do with this noise?

I've tried to attach 2 sound files with the noise playing, I keep getting an error invalid file extension? I have it in MP3, 3gp, and wav formats, it won't let me attach any off them.

Thank-you,
Steve K.

Hi Steve,
AVC disable is not extended out of the amp--that pin is for factory use only, during production testing---
Have you attempted to feed anything else into the amp ?--might try a transistor radio--to eliminate cart, and wiring problems ---Ron Rich

Hi Ron,
I haven't tried to do that, would a CD player work? Plug into the RCA's on top of the AMP?

Steve K.

Hi Steve,
Some do, some don't-gotta have the correct ear-phone to RCA plugs, and MUST keep volume low on player--increase it gradually--phono volume mid-range--Ron Rich

Hi Ron,
Used a regular CD deck, like you use with your home stereo receiver, volume on the Juke low, played a record to turn the amp on, the CD played through the AMP but all scratchy and distorted, I could hear the music but not real well. It sounded like blown speakers, but they're not. Must be in the AMP somewhere.....
Steve K.

Steve, directly connecting a CD player, tuner or other item like this will not work properly. As I mentioned the input stage bias depends on the impedance (approx 500 ohms) of the phono cart. A typical player-tuner will look like an open circuit to the amp input and the first transistor will be way out of bias and become non-linear and distorted. This can lead to a lot of confusion. A matching network of a 500 ohm resistor across the input and an approx 100k/ohm resistor in series with the source. Otherwise, the best method is the actual pickup or an external turntable w/magnetic cart.

A line level signal can be inserted at the high side of the volume control. Always remove the mech mute-trip plug for all tests. that way it is not necessary to power the mech.

If the distortion is common to both channels DC voltages are the first step in troubleshooting.

Rob-NYC

Hi Rob,
When I read your post it reminded me of the impedance of the cartridge when we left off earlier. I went out and got the cartridge out of the jukebox and tested each channel, I got 480 ohms on the right side but no reading on the left, so is that causing the problems with the distortion and very little sound? Is the cartridge bad?
Thanks for your help,
Steve K.

I got 480 ohms on the right side but no reading on the left

If you read this at the cart pins it does mean that the cart is defective --but if the stylus is at least usable there should be sound from the other channel. As for measurements, anything in the 400-700 ohm range should be fine.

If possible, connect either an external turntable w/magnetic cart to the amp, or the mech RCA audio plugs to the input of an amp-receiver with a magnetic input.

Rob

Hi Rob,
I tried your suggestion, connected an old 60's era Zenith (VM) turntable to the Amp and got nothing when playing a record. I turned the volume on the juke all the way up and still nothing? This seems to be getting more and more complicated...any ideas on how and where to proceed will be appreciated.....
Thanks for hanging in there with me,
Steve K.

Steve, does that turntable have a -magnetic- cart in it? Most of those Zenith and VM changers were ceramic and that will just be seen as an open circuit to the amp's input. In a "normal" amp input it would be overdriven by the higher output from a ceramic -not likely here.

Do you have any resistors in the 400-800 ohm range that you can temporarily solder across the amp inputs? That would at least get the first transistor forward biased so that an input will produce "something".

BTW: Have you checked the basic power supply voltages in the amp?

Rob

Hi Rob,
Yes, that's a ceramic cart., didn't realize it at the time, that's the only turntable I have. I have 470 & 680 ohm resistors, 1/2 watt and 1 watt, just tell me where to solder to, under chassis ? From the + to the - on the bad channel?
Have to step out for 1 hour or so, will do as you say when I get back.....
Thanks again,
Steve K.

Steve, just tack solder (temporarily) from the center RCA contact to teh adjacent ground contact.

Wattage is unimportant, The resistances you have are fine. Do both channels. Then you can try plugging in something with it's own volume control such as an Ipod or phone and see what sort of sound you get. there will be a bit too much bass due to the phono equalization, but if you don't overdrive the amp input it should be clean.

Also, on the center board above the two preamp-driver boards, there are sets of diodes. If they are gray rectangles with red or yellow tops, these are selenium and must be replaced with silicon diodes (two on each leg). If they are small black cylinders -they are silicon diodes and "should" be fine as-is.

Rob

Rob,
If "someone" has not changed the AVC board, the "diodes" in a TSA-10B will be the small black ones !--HOWEVER,
They are NOT "diodes--they are stabistors, and are prone to intermittent failure. Ron Rich