Repairing a one arm bandit, need some help testing / identifying components.. - Page 1
Forum section: electronics / beginners

author: insertcoin
author_rank: Contributor
timestamp: August 26, 2022, 05:42:06 pm
content: I have a 1978 Aristocrat Quadreel slot machine which I have been fixing up. I have mostly sorted the mechanical side of things, and now I would like to get the electronics working. Specifically, the coin hopper functionality.At present, wining combinations / jackpots do not trigger the coin hopper to activate and dispense coins. I have been going over the wiring / printed circuit boards looking for faults and I have found a couple of things which need to be addressed.Firstly, I have a relay labelled 'V23003-B0037 B110'https://www.datasheets360.com/part/detail/v23003-b0037-b110/-5176004078453682798/It appears to have become hot, judging by the discoloration on the pins / socket. I would like to be able to test the relay, but ultimately, I know it needs to be replaced. Searching google turns up very little as the relay has been discontinued.Is it possible to replace this with an alternative? Or is there a more reasonable market to buy such discontinued relays, everything I have turned up so far has been $200 - $500.Any guidance is appreciated.

author: fourtytwo42
author_rank: Super Contributor
timestamp: August 26, 2022, 05:50:04 pm
content: Thats just oxidization with the passage of time, no overheating involved. It is possible the switching contacts are in a similar state that can depending on what there used for lead to malfunction. The best solution for both problems is an aerosol contact cleaner. If you remove the relay cover be very careful to slide it off without damaging the contacts.

author: insertcoin
author_rank: Contributor
timestamp: August 26, 2022, 05:53:33 pm
content: I also discovered this capacitor (?) which has self destructed.It is labelled;10+35V+The green plastic outer case has cracked / deteriorated, I assume it has swollen. I am not really familiar with this style capacitor, do I simply replace it with another which has the same 10+ / 35V+ markings?I should mention, that this machine has no service manual / schematics available. There is a fair bit of history on the internet of people searching for info and asking the manufacturer for help, but being told that any manuals were discarded years ago

author: wraper
author_rank: Unknown
timestamp: August 26, 2022, 05:54:00 pm
content: Those are apparently silver plated contacts. They do tarnish over time, it's normal. It's tantallum capacitor, those tended to short/explode. Usual aluminum electrolytic should be fine.

author: insertcoin
author_rank: Contributor
timestamp: August 26, 2022, 06:15:40 pm
content: Thank you both for the quick responses..I had considered that the discoloration may be tarnish / oxidization, but I compared the socket / pins with relays on the same board and they looked fine. Perhaps they don't have silver plating, which would explain it?I will pick up some decent contact cleaner tomorrow and clean the relay and the boards. I will see if I can find a replacement capacitor also.Once I have cleaned the relay, is there a way to test it? I have a multimeter and not a lot else. I would need to energize the relay and test each switch I assume? There's no short cuts?

author: wraper
author_rank: Unknown
timestamp: August 26, 2022, 06:19:27 pm
content: Different sockets. Other 2 sockets are likely tin-lead plated.

author: james_s
author_rank: Super Contributor
timestamp: August 26, 2022, 08:01:14 pm
content: That relay looks fine to me, why do you think it needs replacing?The capacitor is a 10uF 35V type, it definitely looks bad, classic failure mode. Replace it with any similar style 10uF capacitor with a voltage rating of 35V or higher. An aluminum electrolytic would probably work fine too.

author: insertcoin
author_rank: Contributor
timestamp: August 27, 2022, 12:47:51 am
content: Quote from: james_s on August 26, 2022, 08:01:14 pmI thought it had become too hot! I am very relieved that you guys think otherwise!I am just about to head to pick up a replacement capacitor and some contact cleaner. Then settle in for a big day of testing / tracing.

author: insertcoin
author_rank: Contributor
timestamp: August 27, 2022, 04:24:55 pm
content: Quick update, after replacing the swollen capacitor, and spending some time cleaning each board and the tarnished relay, I re-assembled and I now have a hum / low buzzing noise, which I assume is probably coming from one of the relays on one of the boards.The humming stops when I disconnect the centronics cable from the slot machine mechanism. All of the microswitches on the mech connect to the IC boards via a single centronics plug, which allows you to remove the mech from the slot machine chassis.I have also found a couple more Tantalum capacitors which look like the are ready to pop. So I will work to replace them, and continue to map out the wiring and trace it back to the boards.

author: james_s
author_rank: Super Contributor
timestamp: August 29, 2022, 02:05:32 am
content: There is not usually any visual indication that a tantalum capacitor is going to fail, they just go short circuit and go bang. Do you have a schematic for the machine? That would be very useful. The place to start is checking all of the power supply voltages.

author: insertcoin
author_rank: Contributor
timestamp: August 29, 2022, 02:53:56 pm
content: Hey guys, I need some help identifying these diodes.Is it a 6A6I or GAGI ? Nothing matching is coming up when I do a google image search.Or can anyone help with a name of this type of diode?

author: insertcoin
author_rank: Contributor
timestamp: August 29, 2022, 03:10:35 pm
content: Quote from: james_s on August 29, 2022, 02:05:32 amGood info, thanks,There is no schematic for this machine unfortunately, the manufacturer claims that all paperwork relating to this model has been thrown out.

author: james_s
author_rank: Super Contributor
timestamp: August 30, 2022, 12:45:12 am
content: Quote from: insertcoin on August 29, 2022, 02:53:56 pmThey look like fairly ordinary diodes, I've seen that case style occasionally in power supplies and TVs and stuff in the 80s. Do you have reason to suspect they're bad? Check them with a diode test function on a multimeter and if any of them test suspicious lift one end from the circuit and test them again. Diodes can fail, but usually they're pretty reliable.

author: insertcoin
author_rank: Contributor
timestamp: August 30, 2022, 05:49:37 am
content: Quote from: james_s on August 30, 2022, 12:45:12 amI have tested all the diodes on all of the boards using the diode test function on my multimeter and one of these style diodes had a fault.

author: insertcoin
author_rank: Contributor
timestamp: August 30, 2022, 05:58:29 am
content: I need some help identifying a transistor.I have tested all the transistors using the diode test function on my multimeter, and I have found a few failures.Most of the transistors are BC547 and BC549, on the boards, but there is only one of these and it has failed.I am unable to decipher the number after MCR.I have spent some time searching google, for MCR 103 and 108 and I am not finding this particular style of transistor. I don't know if its PNP or NPN, I am hoping that it is familiar to someone. Or is it that the important part is 'MCR'? And any MCR transistor of this style would work?

author: gamalot
author_rank: Super Contributor
timestamp: August 30, 2022, 06:32:12 am
content: Search "Motorola MCR103"https://pdf1.alldatasheet.com/datasheet-pdf/view/4631/MOTOROLA/MCR103.html

author: insertcoin
author_rank: Contributor
timestamp: August 30, 2022, 10:18:02 am
content: Quote from: gamalot on August 30, 2022, 06:32:12 amThank you! I would never have found this.Now that I look at the picture again, I can see the first M, is in the Motorola font.

author: james_s
author_rank: Super Contributor
timestamp: August 30, 2022, 05:44:47 pm
content: Quote from: insertcoin on August 30, 2022, 05:49:37 amCan you tell how it's wired in the circuit? Do you know what sort of voltage is involved? I wouldn't think you'd need anything special like high speed in that application, something like a 1N5402 might work.

author: pcprogrammer
author_rank: Super Contributor
timestamp: August 30, 2022, 07:15:04 pm
content: Looking at the photos some of the diodes look like connected across the relay coils to suppress the voltage when the relay is released. Probably some 1N4000 series diode could do here.But that is just a guess based on what I see.

author: insertcoin
author_rank: Contributor
timestamp: September 18, 2022, 07:52:23 am
content: Quote from: james_s on August 30, 2022, 05:44:47 pmStrangely, I cannot find the diode which I had thought was faulty. I was positive that I had marked the faulty diode, but now I cant find my mark, or a diode which is 'faulty'. I will keep looking, perhaps I was mistaken.The voltages are all over the place. 24VDC / 5VDC / 24VAC / 12VAC..Heres a picture of the power supply, it has at least some detail. Though I would like to know what 'I.C. Unit RI.' means,I have to trace every wire, and work out what controls what.

author: insertcoin
author_rank: Contributor
timestamp: September 18, 2022, 08:04:09 am
content: So I have spent about an hour now trying to replace a transistor, I have replaced a couple already and they test OK.I am either destroying the component with heat, or my test method is flawed.I have NPN transistors, and I am testing using the diode test function on my multimeter. When I test, I place the positive probe on the 'P' or centre leg, then touch the negative to the 'N' legs on either side, If I see a reading of 6.9 and 7.0 on the opposite leg, I believe that is good.However I have one transistor location which keeps testing OK on one leg (6.9) and when I test the opposite, my multimeter makes a tone, as if I were testing in continuity mode. The multimeter display reads OL. I replace with a new one, and I get the same result. Before I destroy my last couple of transistors, can I get some input.I have tested the traces that I am soldering to, and there is no connection between P and N when the transistor is removed.

author: insertcoin
author_rank: Contributor
timestamp: September 18, 2022, 06:21:33 pm
content: Ok, so testing a transistor whilst soldered to a board can give strange results. Disconnecting one leg, the transistor tests OK.

author: james_s
author_rank: Super Contributor
timestamp: September 18, 2022, 06:31:01 pm
content: Testing anything in-circuit can be tricky, it helps if you have a schematic and can see how the circuit is wired and how surrounding components could affect the result. I usually do an initial test in-circuit and then remove anything that gives me a suspicious reading for further testing.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 18, 2022, 06:34:33 pm
content: Yes, you got that right. In circuit measurements depend a lot on how things are connected. My transistor measure knowledge sunk very very deep, and nowadays I just stick it in my component tester after taking it out of the circuit.When it fails with a simple component swap and to understand what is going on, I try to reverse engineer things back to a schematic before doing further repairs. Gives a better understanding of what is wrong.

author: richnormand
author_rank: Unknown
timestamp: September 18, 2022, 10:59:55 pm
content: On your picture of a damaged capacitor (suspected tantalum).Check if there are any others on the board before doing anything else.They are notorious for failing short and sometime taking the power supply with them. Many time without any outside visible indication.In this year alone I found one that collapsed the inverter power supply in a Canberra Series 10 portable MCA and another one in a vector display from Tektronix.In both cases they were not anywhere close the the PSU but in the logic circuits of various modules. Then you can hunt for collateral damage.So before doing anything else I would do a careful survey of the whole unit and use a DMM to check for shorts each one of them. No need to remove them at this time, just do a go-no-go resistance measurement of each one you find.Good luck with it.

author: insertcoin
author_rank: Contributor
timestamp: September 21, 2022, 03:30:18 pm
content: Thanks everyone for the input.I have a couple of tantalum caps left to replace, I have had some trouble getting the same uF /Volt rating. I have replaced about 20 green caps, and I have discovered a couple more bad capacitors, so its time to place an order but I am having some trouble finding a supplier of a 25V 2500uF axial capacitor (first picture), as I understand, this capacitor energizes the payout circuit until all coins have been dispensed or, maybe thats the job of the miniprint caps? Either way the capacitor is dead, Can I use a higher rated capacitor? Or run two lower rated caps in parallel?I also have a couple of these miniprint film capacitors, one sits on the board which has all the different power supply relays, the other is a larger one which sits on the board attached to the coin hopper drive motor. Can someone explain what these do that is different to a regular cap?And finally, I have three, green caps, which to me, look like they have had a big weekend, the text is blurred, I cant work out what these are meant to be. They are bigger than the other green caps I have already replaced.

author: pcprogrammer
author_rank: Super Contributor
timestamp: September 21, 2022, 04:19:45 pm
content: Higher voltage rating with the same capacitance, yes no problem. Two capacitors in parallel only do something for the capacitance, not the voltage rating.To increase the voltage rating they can be placed in series, but might need leveling resistors. Also the capacitance drops.Edit: In parallel the capacitance adds up. So two 100uF in parallel is 200uF. The lowest voltage rating of the two is what counts.Edit:https://www.khanacademy.org/science/physics/circuits-topic/circuits-with-capacitors/v/capacitors-series

author: agent_power
author_rank: Regular Contributor
timestamp: September 21, 2022, 05:52:04 pm
content: Quote from: insertcoin on September 21, 2022, 03:30:18 pmDon't replace too much at once to avoid introducing other issues...the miniprint caps are safety capacitors (X, Y class depending on at which mains voltage line they sit) for filtering noise in and out of the device. Replace them with the appropriate safety rating and class (and lead spacing):https://www.allaboutcircuits.com/technical-articles/safety-capacitor-class-x-and-class-y-capacitors/If they aren't visibly cracked you could leave them alone, but the RIFA variety of those like to go up in smoke and cause a literal stink as they age.For the weird values like 2500uF that aren't available anymore, just go up or down one step as most capacitors have 20% tolerance anyway:https://www.rfcafe.com/references/electrical/capacitor-values.htmOnly go down in voltage if you're absolutely sure your circuit doesn't sit too close too the specified value already. Better same, or slightly higher (but not too high as ESR rises with voltage)Enjoy, looks like a fun machine to repairPS: If there are socketed ICs you can spray the pins with contact cleaner and/or re-seat them, this can solve erratic behaviour as well

author: james_s
author_rank: Super Contributor
timestamp: September 21, 2022, 10:52:45 pm
content: Generally I'd say if in doubt, go up in both capitance and voltage if the original value is not available, that's almost always safer than going down. You can generally go as high as you want in voltage rating and the only limiting factors will be cost and physical size. Due to the wide tolerance of electrolytic capacitors you can usually go up at least +50% in capacity without issues, sometimes more. Electrolytic capacitors are usually used for smoothing and DC blocking where the value is not critical.