Continental AMI Juke Box Fault Finding

[rob1948]

Hi Ron,
Thanks and yes I have read the FAQ re contact cleaning and just read it again. As I expected I switched on the JB but still have the same problem, scan magnets not energising and also the selection solenoid !!! Sprag Relay and Pulse Control Relay Must be the contacts on either relay ?? I changed the 100MFD capacitor, but I was taught that if something does not look right it is not right and this 'stupid' looking minute 100MFD capacitor I have installed does not look right. Any way be that as it may, and having read the contact cleaning FAQ again let me go and do some more work on the Sprag and Pulse control Relay contacts.
From reading the Service manual, I have made the following operating sequence notes; Once a record selection has been made, the operating sequence is as follows: Sprag relay contacts close; Scan magnets in Scan Controller energised; Selection Solenoid extends pin for selection; Scan Switch closed; Record Magazine Motor turned on. So from Norman's post and having replaced the 100MFD capacitor the problem can only be the relay contacts ?? Will go and check the contacts once more. Thanks Rob.

[Ron Rich]

Hi Rob,
What "looks wrong" about that 100 uf cap (what does it say on it ?) ? Is the sprag relay energizing-- to close the contacts ?

[jukenorman]

Rob,
Also is the pulse control relay energised before you make your selection? 100uF, 50V elecrolytics are quite small these days (about 8mm dia. x 11mm typically)!

Norman.

[rob1948]

Hi Ron/Norman,
The physical size of the cap looks wrong, but it is right and marked 100uF and 50V. It is 8mm in diameter and 16mm in length as Norman confirms.
As far as the operation of the sprag relay and pulse control relays are concerned I observe as follows: When I push the cut off switch (toggle switch) forward the latch solenoid pulls in, latch relay energises(credit available) and the pulse control relay also energises, no record selection made. Record selection made and the search unit rotates, selection made, search unit stops, pulse control relay de-energises/re-energises instantaneously (because credit is available) and the sprag relay pulls in and drops out instantaneously. And this is where the operation STOPS ! I then manually push the selected record pin(s)in and then lift the large gear bracket up to the two magnets in the scan control assembly and the cycle continues until the record is placed back in the record magazine. Obviously something is preventing the two magnets in the scan control and the selection solenoid from energising Sprag and pulse control relays appear to be operating correctly so can only be 'burnt' relay contacts ?? I note some sparking at the relay contacts ? I hope this throws some more light on the problem. Thanks guys.Rob

[Ron Rich]

Rob,
Check the NO contacts on the sprague relay-- see the sticky on "contacts-continuity checking", in the FAQ's-- Ron Rich

[jukenorman]

Hi Rob,

The sprag shouldn't immediately drop out - it's held energised by a 47 ohm 7W resistor after it pulls in, see the diagram on page SSS-26. You should maybe check that resistor? The pulse control relay shouldn't de-energise either, it should stay energised for 100 milli seconds after the sprag relay comes in, held by the 100uF capacitor. There's a resistor in series with the 100uF capacitor, maybe check it also - although it would appear not to be open circuit, otherwise the capacitor that was connected the wrong way round wouldn't have popped!

Edit - the pulse control relay de-enegising might be the nub of the problem because that will pull in the latch solenoid which will release the pushbuttons dropping out the sprag relay.

Norman.

[rob1948]

Thank you Ron and Norman for this feed back !! I was also thinking that a resistor(s) could be the problem ? Thanks again, we will get there.

[rob1948]

Hi Norman/Ron,
Thanks again for your assistance. This is where I am at; Sprag Relay- capacitor replaced and resistor checked (with my analogue avo meter) and measures 50 ohm. Contacts cleaned and continuity checked - all ok. Pulse Control Relay - new 100MFD capacitor fitted and resistor checked and measures 100 ohm (very small resistor) all ok. However the 'terminal strip assembly' also has two resistors in circuit, colour coded with 5 rings identifying the resistor size.(physical dimensions 50mm x 16mm). Because of age, the ring colours are not that clear - brown-grey-yellow-grey-blue. One resistor is open circuit (could be the problem ?) and the other reads +/- 4-5 ohms. These resistors are not shown in the phonograph schematic and therefore I can't pick up the size of the resistor. Could you please help with the size of these two resistors as I want to replace both of them. Thanks Rob

[jukenorman]

Hi Rob,
These are not resistors, they are capacitors - I think we already mentioned these old capacitors with colour bands. I wondered whether it might be two capacitors in series to make up the 0.25uF that is across the two R2 contacts that are in parallel but it's very much a guess! In any case, I doubt whether they are the cause of your problem. Maybe you could trace the wires from them?

Norman.

[rob1948]

Hi Norman,
I would like to send you a photo of the 'terminal strip assembly' and you will then see exactly what I an talking about. Pictures tell a 1000 words. Would you like to share an e mail address with me or is it possible to paste the photo on this post ?? Thanks Rob

[jukenorman]

Hi Rob,
It is possible to post pictures here but I will message you an email address anyway. I did take a look in my Continental and I was pleased to note that I had changed the 100uF electrolytic but the remainder of the components on the terminal strip were original. The lead from one of the capacitors went up to the Sprag and the lead of the other went to the PCR (R2) which is why I thought that they might form the 0.25uf that's across the R2 contacts.

Norman.

[rob1948]

Hi Norman,
I replaced the 100MFD capacitor which has a indented ring on one end identifying the + end. A second and original capacitor 0,047MFD is next to the 100MFD with a orange ring on the one end which Ron said identified the 'most negative end' and these two capacitors appear to be connected in series ? The other two capacitors or resistors both only have coloured rings on them 5 off. Capacitors normally have their size and voltage marked on them and resistors are identified with colour rings ? The small 100 ohm resistor has colour rings on it and so this is the reason I assume these are two resistors and not capacitors ? Rob

[jukenorman]

Hi Rob,
There is a picture of the terminal strip - these are all capacitors. The pink one is the 0.047uF (or 0.05 on the schematic), the small blue one is the 100uF electrolytic and the two at the top, I think, form the 0.25uF but I am not certain about this.

The brief sequence of events should be:
Buttons pressed, selection found, Sprag pulls in.
Sprag contact in PCR coil circuit opens but PCR holds for 100mS because of time delay capacitor.
During 100mS when both Sprag and PCR are both energised, pulse sent to selection solenoid and scan solenoids.
PCR drops out, energising the latch solenoid via the latch relay, buttons release, Sprag drops out.

My gut feeling is that you have an issue with the time delay on the PCR. I also cannot see anything common between the 100uF and the 0.047uF capacitors that would make them appear to be in series. At minimum, there should be a contact of the Sprag between them - and that's with the 100 ohm resistor on the other side of the 100uF cap compared to the schematic.

Norman.

[jukenorman]

Hi Rob,
I don't seem to be able to edit my last post - I just wanted to say that if the time delay components are wired to the wrong side of the Sprag relay contact, then that would certainly prevent the time delay taking place.

Norman.

[rob1948]

Hi Norman,

Sorry post above, pushed the wrong button. Thank you very much for this photo and the brief sequence of events. Yes that is exactly what my terminal strip looks like. You have given me more than enough info now to carry on with my 'trouble shooting'. I will check the wiring of the time delay components to the sprag relay. Should I replace the two top black capacitors or maybe not ? Thanks Rob

(EDIT: I deleted the incorrect post-- moderator)