[Jukebox-list] Wurlitzer 2600 Sound update

[Ron Rich]

Hi Iain,
  I suspect that 127vac is a bit high, (max allowed here is 125vac)  however it does not account for the voltage readings you are getting. Most schematic readings are aproximate however, unless they specify the exact AC input voltage and the exact type/brand of meter that they used for those readings--and you have the meter to match it. 
  I would first change the 5U4 to see if the readings change--If not, I would suspect that something is wrong in the power supply--
  You may very well have a problem in that RC package--in which case you will need to build one to replace it--but like you said, get the voltage readings down first--
  Not having a schematic--that 4k / 5k  resistor is suspect-- 
  The 5 watt resistors do run very hot, and will appear to be "cooking" if anyone has ever "sprayed" them with "contact cleaner", or any oily type product. Did they check out at 310 ohms? If so, I would guess them to be OK. If I am correct and the output tubes are 6973's, they also run very hot--watch them for "purple flairs"-- If you see the flairs, they are shorting--
  either a sign of a bad tube or bad coupling caps---( or too a high voltage? in this case).
  Ron Rich
  

Iain Jamieson <pinballrepair at paradise.net.nz> wrote:
  Hi all,

Well, I tried running a new earth from the preamp back to the transormere earth. I also discovered that the squeal noise that comes on after about 5 minutes will go away if the trebble is turned down to a minimum in the B channel. looking at the schematic, the trebble control goes into what is called a P.E.C 112231. A flat package that contains caps and resistors. These are original and was wondering if these could be the problem. However, I discovered something else and was alerted to a burning smell. The 5 watt 310ohm resitors that go to pins V7 - 7, V8 - 9, V9 - 7 and V10 - 9 were cooking themselves. I replaced these and did some voltage measuring on the these Tubes. These are the voltage I got. In Play position V7 - 9, V8 - 7 have 427v DC instead of 380v. In Rest I get 44v DC. On V7 - 1 and 8 read 302V instead of 265v. In rest I get 37v These voltage start higher and stabalize to the above voltage in about 40seconds. Having a look through the schematic, I found a
 resistor that was a 4k, instead of a 5k, so will replace that tomorrow. We have 240v line voltage here, going through a 117v secondary transformer that is outputting 127vac. Would like to check this first before looking into the squeal issue, but it could all be related? Those power amp tubes get fairly hot. Any advise here would be appreciated. Cheers Iain
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