6100 HV troubles

komodo

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Donor 2019, 2021
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I am losing my touch. I've worked on 4 different HV cages over the last few weeks and all the repairs I have done to them are starting to run together. I really should keep a log of EVERY repair I do to EACH HV cage so that I can remember what I have and haven't done. I have 2 of them working finally but the current one I am working on is giving me fits.

The issue is that I can only adjust the HV down to about 21kv. Pin 5 of the HV cage reads 230 volts. The HV unit was rebuilt with new parts and upgraded per the FAQ. Numerous burned resistors and dead transistors were replaced and torn pads were jumpered. Despite going thru the entire cage, I still can't get it to work correctly.

Please take a look at the values for the transistors listed below and see if you can't help me pinpoint where the issue is. Voltage values are all DC voltages (obviously) and are listed in the following order.
Collector Base and Emitter
\
Q900 23.25 18.5 17.9

q901 23.2 18.4 18.3

Q902 18.8 15.62 15.04

Q903 22.86 16.21 15.67

Q904 -15.1 -22.6 -23.24

Q905 22.2 -23.1 -24.0

Q906 17.5 -24.8 -23.7

I have been all over this particular cage and checked the transistors several times along with diodes and resistors. I will move onto the last cage awaiting some help from the gurus out there.
 
Haven't been home to work on these yet. Just a bump to let you know I intend to follow up as soon as I can.
 
Well, this one turned out to be okay. I think I changed a 555 on it and forgot to test it afterwards. Talon2000 says it is fine. The other HV I was working on I gave up on. Talon2000 found a burned resistor and the 555 was bad on that one although it tested good on a tester. (Failed under load) I had checked every resistor about 5 times so it might have overheated and burned as a result of the 555. I don't know for sure. Glad to have these both up and running now.
 
Well, this one turned out to be okay. I think I changed a 555 on it and forgot to test it afterwards. Talon2000 says it is fine. The other HV I was working on I gave up on. Talon2000 found a burned resistor and the 555 was bad on that one although it tested good on a tester. (Failed under load) I had checked every resistor about 5 times so it might have overheated and burned as a result of the 555. I don't know for sure. Glad to have these both up and running now.

Great Pat. Do you mind if I link to this fault on my WG6100 site please? :)
http://www.dsbelec.iinet.net.au/Wg6100_Dezbaz.htm
 
Has anyone tried the 7555 timer IC to replace the 555?

The 7555 is CMOS and has different timing characteristics - it's also what you get when you buy a 555 chip at Radio Shack. It doesn't work well in the audio circuit of Galaxian as it changes the pitch of the sounds so I wondered if it would be out of whack on the HV board too.

RJ
 
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