Phonoland

My first juke was a LPC1. I rebuilt the amp about 13 years ago, replacing everything except the transformers and mute relay. I've never been happy with the sound - bass is very boomy and distorted, almost like it's being overdriven.

When I was doing the rebuild, I noticed some of the resistors had different values that what was called for in the schematic. At the time I chalked it up to production changes that never made it back to the drawing.

I guess my question is did that kind of thing happen where the schematics were not changed, or should I go back and replace those parts with what was originally called for.

Thanks
Don

Don,
The TSA-1 was Seeburg's first "transistorized" amp, and there were many "updates".
Find a "Code F" schematic, and use the parts listed there, for the "best" sound--but remember one thing, the LPC-1 was designed to use "DS" speakers, and will never, IMHO, sound "real good" without them. Ron Rich

Thanks for the reply Rich. I will see if I can find that revision of the amp schematic.
I've been looking for some DS speakers for awhile. They are few and far between, and when I do see them, they're usually more than what I paid for the juke.

MrGorf wrote:My first juke was a LPC1. I rebuilt the amp about 13 years ago, replacing everything except the transformers and mute relay. I've never been happy with the sound - bass is very boomy and distorted, almost like it's being overdriven.
Thanks
Don

Don, these were, at best, mediocre amps ..but they should not sound 'overdriven'.

The most likely cause for this is inoperative AGC. The gain structure of that, and most juke amps requires that the AGC circuit keep the level coming out of the preamp at a point lower than what will overload the following stages.

The package rectifiers in that section are selenium and are -always- deficient by now. Even in the mid- 70's these amps were exhibiting the sorts of problems you describe.

CR103, 104, 105 Must be replaced. For C105 any small signal diodes can be used -one for each leg. For C103 1nd 104 You should use small signal diodes and use three in series for each diode shown. These diodes control the level and modern silicon diodes have a much lower internal resistance than the selenium originals. If you use only one in each leg the attenuation will be too strong and the low impedance may cause some non-linearity in the circuit. Three in series is the perfect sub.

There are simple mods that can greatly improve high frequency response, which I'll go into if interested.

BTW, Are you using the original pickup cart. these amps rely on the DC resistance of the pickup across the the input to properly forward bias the first stage. Goofy, but using a later cart will cause muddy, distorted output due to this.

Rob/NYC

I remember when I rebuilt the amp I replaced those back to back diodes (I think I used 914's because thats all I had), but it didn't sound good so I put the original ones back in.

As far as the cartridge, I did buy a replacement, but while I'd been working on it I put the original back in.

What would be a good diode to use to replace the AGC ones.

Thanks
Don

Don,
Any "signal" type--914's should do it--but do, series wire them as Rob suggested.
Ron Rich