Mech wants to go beyond selection 179

Hi,

Today I hooked up the mech to the rest of the SMC-1 Jukebox.
When I power it up it goes to it's 100 position and the CPU boots.

Now when I make a selection, say 100, or 200 the Mech goes to the right position (CPU counts up) (179) and it keeps on going when it hits the limit switch.
The 179 limit switch is working, and I backtracked it to the MCU and the PCC1 module. Both receive the limit switch.

It's not clear to me yet who controls what. I think the PCC1 should change the direction of the Motor when it hits the 179 limit switch.
Is this true?

In other words. Should I be looking at the PCC1 or the CPU?
Any pointers as to where I should look?

ps. When I power down the juke, and then up again The mech goes to it's 100 position again and stops there.

William,
What you have asked is the classic "which came first--chicken/egg" question.
Basically, The MCU is the "master computer" that issues orders to the PCC, which in turn issues orders to the mechanism. However, once issued, the MCU waits for a reply from the PCC, which is also waiting on a reply from the mechanism. If the mech fails to preform the command requested, the PCC just waits--so does the MCU.
In your case, I am GUESSING, that you may have multiple problems. I have not worked on the original MCU's in 30 plus years--and sure will not today. I have (and always have had) the advantage of having several known good PCC interface boards here--which make it rather simple--even more so today, with the Gen 2 MCU, to trouble shoot the mech and PCC. About 80% of the time, this problem is the MCU, about 10% the PCC, and 10% the mech -
Good luck--Ron Rich

Hi Ron,

The advantage of having several working parts around to rule out some possible problems is great indeed!

Lets take it a step back.

What should happen when I press 100 and the mech is already at 100
Should it pick the record immediately and start playing or should it go scan to 179 and then back to 100?

When I select 110
Should it go to 110 and pick up the record or should it go to 179 and then back?

I'm looking for the procedure of picking up a record so I can start thinking and looking at the schematics to find out when the controls lines like
Play A, Play B, Motor On etc etc.

Most logical would be that if I select 110 the following should happen:
Motor on > play a > (count till 110) > trip relais > pick up record

Forgive me if I'm wrong It's the first jukebox I'm trying to figure out But I love puzzles like this

Thanks again Ron for your answers!

Well, I found one problem. It's on the PCC. U1 is not working correct. SO I replaced it and now we get a little further.
It boots up, mech goes to the left and it awaits input.

There are now 3 scenarios:

select A side of any record:
Mech goes to the right, hits limit switch 179, goes back and plays the correct record.
Record finishes > Record Ejects, Mech goes to the right, Hits limit switch 179 and stops.
Any further input is now ignored, nothing happens.

select B side of any record:
Mech goes to the right, hits limit switch 179, goes back and plays the correct record.
Record finishes > Record Ejects, Mech goes to the left, Hits limit switch 100 and stops.
Any further input is now ignored, nothing happens.

Select 2 records:
Mech plays only the last one I entered

These sound like strange errors. Could be memory problems on the MCU?
One thing points to another problem at the PCC, the Motor is still a little bit powered when it hits the limit switch.
It's as if the PCC "hangs"

William,
Impossible to tell from here--guessing--both are problematic--PM me if you want me to rebuild the IFB, or purchase a new Gen MCU----
Which IFB is in the PCC--Brown-rev A, Brown Rev. AB, Green A,AB? , Green rev B, or Green rev C ?
Word of advise--If you have not done so, oil that motor, with 20 wt. ND oil, before running it any more--
Ron Rich

I know it's a difficult problem to solve using forum posts
But 1 step at a time I'm getting there.

it's a REV A, brown.

Some general questions then:

could you answer these general questions then please?

When a record is done playing and no other selection has been made. What does the Mech do? Just stop or will it go to 100 / 179 ?

When I enter two songs, will it start playing the last one I entered first or the first one it encounters while scanning?

Thank you for your time Ron, and rest assured I will buy that new CPU from you
(ps would it matter to you if I buy it here in the netherlands or is it better to buy it from you ? )

Hi William,
Careful on those brown boards--bad traces--use a low heat iron ONLY--
Depends--do you have the two blade type limit switches, or the three blade type ?
First encountered, except if record 00, or 79--
I would prefer to sell it, directly.
Ron Rich

I have the two blade limit switches

Could you PM me the price including shipping using paypal for the MCU2 ?

William,
With the two blade style switches, and the "old style MCU", the motor should shut off after playing the last selection.
Ron Rich

Thank you,

I made progress again, I found another cipf at fault in the PCC. This time it was U12, the quad NOR gate.
This chip is partly used to signal if the mech is going from play to scan mode. The outputs of 2 of the gates where always 6Volt.
Thats a good sign something is wrong as it should either be 0, or 12V (supply)

So now that this is fixed, the mech and the juke seems to be working. But now I found out that the sound is really distorted. I'll make a new post for this.

Thanks for the info Ron!