rock ola 426 write in read out problems

After getting near the end of this resotration this one just wont stay fixed. After going through evey section of the sound system, amp, crossover, volume control speakers, and wireing, I am still getting an intermittant drop out on the right channel. I believe it is at the cartridge and will check it soon but any other suggestions on it would be great.
The big issue is A and B 1. When selected the write in arm cycles and trips. then is starts a search scan, but just goes to home posistion and stops. The pins do not appear to be tripped. When the pins are manualy tripped it works normaly. R8 goes and gets the record and almost finishes the load cycle but shuts down just as the tone arm comes over to the lead in groove. It just stops, eveything, including turntable. the only way to get it to go is to trip another pin, then it plays r8 and goes on to the other pin selection and operates normaly. When we started this project we cleaned and burnished all the wiper contacts on both sides of the pin bank.
3rd issue, just started today, make a selection lights us but the keys wont lock to make a selection. that is also intermittant and after a while they start working again.
the dual speed is also an issue in that after much cleaning and lubricating it will take a mini lp and place it on the turntable, but then the turntable just stops. the idler wheel will not contact the motor shaft at all, it is pulled away. i was not going to bother with it but thought I would throw it on with these other problems to see if it is and easy fix. thanks in advance. Mark

Hi Mark,
Is it possible to swap channels on the cartridge, to trouble shoot it ??
Sounds as if either the wobble plate coil can not pull the plate out of the way ( broken/missing "U shaped copper spring" ?), OR, the hammer coil(s) do not have enough power to move the pin ?
I don't understand what you are saying about "R-8"--- Is that the ONLY selection that does that ( all others normal, when pin is manually set ?). If ALL selections do the same thing--faulty Micro Switch adjustment, or faulty MS.
3rd issue--dirty, or ( something) imbedded in one or more of the leaf switches, in the keyboard.
Ron Rich

Thanks Ron:
i will check the write in wipers again to see if they have a bad section.
it is only R8 that stops the play cycle. all other pins work normaly. Thanks Mark

Stopping hasgottabe--the slip rings/contacts, on the read out side--the "carry over" is not making when R8 plays--
Ron Rich

I am still getting an intermittant drop out on the right channel. I believe it is at the cartridge and will check it soon but any other suggestions on it would be great.

I haven't followed this topic, but I assume you have wiggled all connections, thumped the amp and measured the impedance of the cart to check for continuity. It would be helpful to remove the volume control box and connect a multimeter set to low voltage AC to the high and ground on one channel and them the next. the idea is to narrow whether the pro is ahead, or behind that point. Aside from interconnections, the frequent failure points are capacitor in the coupling chain and small transistors with junction failures. Both of these are generally temperature sensitive.

The big issue is A and B 1. When selected the write in arm cycles and trips. then is starts a search scan, but just goes to home posistion and stops. The pins do not appear to be tripped.

This is odd. I suspect you are overlooking a partially tipped pin that gets knocked back by the readout arm. On the top of the pinwheel is a small "assist solenoid" which is coupled to the internal wobble plate by a "U" shaped spring. these often brake and the write-in punch alone is not enough to allow the pin to fully enter the selected position with this solenoid.

The pins do not appear to be tripped. When the pins are manually tripped it works normally. R8 goes and gets the record and almost finishes the load cycle but shuts down just as the tone arm comes over to the lead in groove

When a record is nearing the T-T three things are happening. A resistor is placed in-series with the gripper motor to slow the arm as it descends. A microswitch on the mech cams takes over and sustains power after the selected pin has been cancelled.

There is no good reason why one selection would react differently than any other in this operation.

Observe the microswitches on the mechanism. Find the one that is changing mode at the point where things die and check that switch.

Rob/NYC

Ron Rich wrote:Stopping hasgottabe--the slip rings/contacts, on the read out side--the "carry over" is not making when R8 plays--
Ron Rich

Ron, there is also a carryover that homes the mech after last selection. Is that included in the micro right by the gripper motor?

This one: http://www.retroaudiolab.com/pictures/e ... echcap.jpg

It is toggled by the A vs B cam track and is the only thing I can think of that could also maintain a scan after pins cancelled and tonearm cam at rest.

Rob

Some models use the "Micro Switch" carry over, others have a ring--don't re-call which one is used, in which model ???
Ron Rich

Thanks for the suggestions. Have not had time to check yet, but hope to have some time this weekend between "honeydo's". Mark

Hi Guys: just wanted to say thanks for the suggestions. This one was such an odd cause I just wanted to let you know what the fix was.
The read out arm has not only the hammers that cancel selections but on the trailing end there is a metal tab the engages the switch that parks the arm when there is no selection. What was happening is the switch was out of adjustment causing the cancel hammer to catch it on R8 so after the load cycle completed, it "thought" it was supposed to be park, stopping the mech dead.
Adjusting the switch solved the R8 problem.
Mark

Hi Mark,
Glad you found it--I guess that you did not understand what I wrote (way) above--the "carry-over switch", is the switch you are calling "the switch that parks the arm". This is why I always scream to use the "terms used in the manual".
Ron Rich