LPC480 with a bum TASU

Ron Rich wrote:Hi Thom,
Don't understand why/how--but both Rob and I, made "typo's" there--there should not be a "K" there--the original pot was 4 ohms !
Ron Rich

'Just shows your powers of persuasion. You missed your calling, you should have been a politician...or ad man.

Rob

Rob,
Funny you should say that--I always wanted to write ad's--wrote a few when I was younger--never made any $$ doing it--Politics--NO! Thank-you--I can not tell a lye--or is that a lie ??
Ron Rich

Gentlemen,

These are some of my readings, all referenced to the frame unless otherwise stated:

Black wire in to L751 - 119 VAC
White wire out of L751 - 119VAC (also White wire in to T751)
Green wire out of T751 to 4uF cap - 119 VAC
Black wire out of T751 to 4uF cap - 119 VAC
Red wire out of T751 to bridge - 5.38 VAC and rising slowly
Red wire out of T751 to bridge - 5.38 VAC and rising slowly
Across C752 (1000uF) - 12.9 VDC and rising slowly
Red jumper - 13.8 VDC and rising slowly - jumper disconnected from post

Some variations due to time between readings should be allowed for.

Thom Smith

Thom,
I am at somewhat of a dis-advantage, as the schematic I have designates different numbers for the transformers--If, you are measuring the two reds from the largest transformer (that go to the 30vDC supply), remove the red jumper and measure across the two reds--should be around 25-30 vac--On 1200 uf cap, to ground--should read 29-30 VDC with wire un-plugged ! If those readings are good, plug the red wire on, and see what the DC voltage does at that point--Ron Rich

Ron, here is a schematic with the same part #'s. I'll hold off giving a final opinion but, I think it is looking like a bad tran.

http://s1192.photobucket.com/user/Rob-N ... rt=2&o=118 Hover the mouse and click the fourth button to blow it up full size.

Thom, when you removed the old diodes in that section did you test them w/ohmmeter? Were any shorted?

Rob

Rob,
Yep --attsa what I'm thinkin' too--but need to see PS readings first--could be a bad anything ??
Ron Rich

Ron,

I'm not getting any reading across the two red wires. Guess I'll be looking for a transformer now. It's a real shame that the USD is so strong against the CDN dollar right now. Makes all of this just a tad more expensive than I'd like it to be. Are there options as far as a substitute goes? Can I work around the 'saturable transformer' setup with something I might be able to find locally off the shelf?

Rob, yes, one of the diodes was shorted. I couldn't tell you which one from the diagram but there was one. I replaced the lot of them with what I had on hand, 1N4004 diodes with a PIV of 400V.

Thom

Thom,
Didja look at the in-coming voltage, is the relay energized-contacts all "making well" --choke (remember that guy) good ?
Ron Rich

Thom, if Ron's suggestions don't pan out, try contacting this fellow -he is in Canada and has been very helpful to people via The Jukebox List:

John's Jukes Ltd. 2343 Main St., Vancouver, BC, Canada V5T 3C9 Call
(604)872-5757 or Fax 872-2010 (Pinballs, Jukes, VideoGames)
www.flippers.com

I have also seen LPC TASU's on E-bay in the $30-$50 range however the weight can add significantly to the cost.

You might also try John Papa - (888) 321-7272 - johnpapa@frontiernet.net
http://www.nationaljukebox.com/index.html He deals mainly with older machines but may have some LPC stuff 'kicking around". I've found him to be honest and pleasant to deal with.

Because of the configuration of that transformer there really isn't any sub for it.
An extreme & permanent solution was to convert the gears to native 45 and eliminate the autospeed. I helped with that on an LPC down on Tenth Ave in 1986. It is not quite a daunting as you might think, but it is a major operation. In our case it was done to eliminate the noise from the speed unit...and we were bored .

Rob

Hello,

Just a quick update.

So, it would seem that a point I missed somewhere along the line was that in order to get the readings that Ron was suggesting, the mech needed to be in play mode, that is with a record loaded in it as if it were ready to play. With the mech in play, the relay energized and the magic happened, that is until the main fuse blew and brought things to a standstill, for now.

When it was running I was indeed getting close to the voltages that Ron suggested I should be seeing; about 26VAC across the two red leads with the jumper off and 32ish VDC across the 1000uF lytic. Sorry for the rounded numbers, the fuse blew shortly after and I didn't get a chance to properly note them. Once I re fuse and fire it up again, I'll note the actual numbers. The problem was that I went to select a different slot and the mech wouldn't stop scanning. Finally it reached the right end again and that's when the fuse blew.

Anyhow, I am encouraged by the presence of the requisite voltages. I am going to have to replace at least one of the 2050 tubes in the TCC so maybe the other one was soft as well and has dropped below functional level. I'm thinking of replacing the 12AX7 tubes as well, just so I know everything is good. I've got a capping kit on order for the TCC and the TSA3 as well. I think I'm going to hold off on more work until those come in and I get everything freshened up.

I'll keep updating as things develop. Thanks Ron and Rob for all the input so far.

Thom

Hi Thom,
Well, what can I say--except, had you read the service manual, or my "Seeburg Mechanism Guide", you would have known that the LPC models are all "native" 33 rpm phonos, that use the Autospeed to run at 45 rpm--
NOW--which, fuse blew ?? Ron Rich