Phonoland

I was doing some work on my SMC1 microcomputer control unit when I noticed the legs on some of the chips were tarnished. I pulled them out to clean them, and when I pulled out the cpu chip about 4 of the legs stayed in the socket.
Anybody know where I can find a replacement? The chip is a Mostek MK14207N. I don't seem to have much luck even finding a datasheet.

Mr Gorf,
I have some--also sell a replacement MCU for SMC phono's-- Contact me off forum-- ronnnrich@yahoo.com
Ron Rich

Thanks Ron - email sent.

OK - after having to take a break from this I finally got some time to work on it. Here is where things stand.
Removed all electronics and wire harnesses to clean cabinet interior.
Replaced all electrolytic caps on amp, PCC and MPU.
Re-assembled all cables and electronics.

When I first turned it on I heard a real loud pop. The funny thing is it didn't sound electrical, it sounded more like relay contacts but was really loud. I didn't see any kind of flash or see or smell smoke. All fuses checked OK.
After that when turned on I could put it in service mode and it would scan when the switch was held. There was no response when coining up or hitting the credit button. The display on the MPU is dark. I turned it off and on again, and the mech tripped and tried to play a record. Since there were no records in the box, the arm moved to the center and it rejected. The mech then scanned all the way to the right and instead of reversing tried to keep going. I turned it off and after a minute turned it back on. Now it either tries to plat the last record on the right or tries to scan past the stop. If I switch to service mode the turntable stops, but the scan switch does nothing. Putting it back to normal mode makes the turntable start up again, but the mech doesn't move.

Not sure where to go from here. Sorry about the long post.

Update.

She's now working.

Turns out the connector for the two regulators in the MCU box was bad. When I pulled the pins out to check them some were so far corroded they crumbled. I replaced the connector and it fired right up.

Glad you got it--one word of advise--clean up the whole MCU, including the metal box. It seams that once the batteries corrode, it just continues to spread "like wild fire"--Ron Rich

Thanks for the advice Ron. I did notice much of the paint is peeling off. I think I'll pull the box and sand it down.

You are welcome--
What did you do about the "broke legs" --and the "pop" ?
Ron Rich

To fix the broken legs I did the following:

Cleaned all of the legs with a fiberglass pencil (breaking a few more of the weaker legs off in the process).
Put the chip into a dual wipe 40 pin socket.
Using the pins from a 'component carrier' (JAMECO 291996) trimmed down, I inserted these into the socket where the broken pins were.
Soldered the replacement pins to what was left of the broken pins on the chip.
Desoldered the original 40 pin socket on the board and replaced it with new socket and chip.

I realize this fix is only temporary at best, but for now it works.

As for the 'pop', I'm not sure what it was. I do know that when I went to pick up the juke, the seller had already brought it up from his basement and mentioned the carrage had slid back and forth a couple of times. Not sure if that had anything to do with it or not.

I just re-read your 1st post---
The "pop" was probably "normal". Most likely, what you heard was "current inrush", thru the speakers, at the start-up of the amp.
This happens when the mute relay is "slow"---there is no adjustment, nor cure for this-- nor is it a "problem"--
As for the chip repair--I have also soldered onto the broken legs--mostly successful, but sometimes the chip "was dead" afterward--
Lotza fun ! Thanks for posting the answers ! (and like I sad earlier--I have new replacement, SMC, MCU's for sale)
Ron Rich