On 3/2/2026 7:46 PM, John Robertson via Jukebox-list wrote:
Hi Tony,
On 2026-03-01 11:55 a.m., Tony Miklos via Jukebox-list wrote:
I don't know a lot about Wurlitzers of this era. I'll start this off with, on the bench, applying 14vdc on the bench power supply to pins 3 ground and the plus to pin 4 of X5, in about 1/2 second, the leds K and Z light up and stay on. Then in another 1/2 second relay 2 energizes and stays on. I don't know if that is a normal power up routine? The SCC is a 2500 CD.
Yeah, that sounds about right. Without the optos in place then Z and K will remain lit. Relay 2 is the Scan relay...You need a DOKTOR BOX to easily test these computers. Want a schematic? Then you only need a display and some buttons, etc.
Now the really weird part. Inside the jukebox, with no cables plugged into the board, from pins 3 and 4 of the plug for X5, it measures about 14 volts DC, no AC, this is normal. But, when that plug is in the SCC on power up, the 14 volts jumps up to 30 volts! Thankfully the 7805 has over-voltage protection, in addition to a zener on the board so the +5vdc goes to zero.
As for the X5 plug, check the schematics, sounds like something is wrong, perhaps in the I-84 Amp where the voltages originate.
I have tried this with all of the plugs in the SCC and with only plug X5 in. Either way the 14vdc jumps up to 30vdc and the +5vdc goes to zero.
On the SCC, it has a history of R3 running hot and turning the board very dark. Also someone cut into the plasic cover in what looks like an attempt to cool the area at and above the 7805 and R3.
R03 is 3K3, it won't run hot, please check the silkscreen for the correct resistor code. I don't know of any resistor running that hot in the 2500 S&CCs, that sounds like something odd is happening.
Also, I don't know if it's common, the interface board top third is very dark from heat. This machine has been on 24-7 for most of its life.
The Interface Board has a long history of cooking those resistors! That is part of the Wallbox hookup and one of the two series 470R resistors can be cut out if you wish.
Any help greatly appreciated.
Hope that helps! Do you have the service manual?
John :-#)#
Sure I'll take a schematic for the Doktor box and see what else I will need to make it work besides a display.
Yes, I have a few manuals with schematics for the credit computer. Again, it is R3 that fried. No doubt about it. I can take pictures if you like. The transistor fried also. It was evident it happened before because I could tell they weren't factory solder joints. I installed the new ones a bit above the board so it doesn't do damage to the board that is already in sad shape. I am guessing that there is an intermittent short that was causing it to burn up. Right now, neither are burning up or running hot. So joy oh joy, it's intermittent. Oh, according to my schematics, it is a 330 ohm resistor, not a 3.3K