verni QUASAR restoration

[PaulSwan]

I've started looking at my own KT-3 in my US Quasar, not much yet but at least pictures of the daughter boards:
http://www.zzzaccaria.com/USBilliardsQuasarRestoration.htm
Paul.

[vernimark]

very detailed, thank you

Yesterday I replaced burned resistors and shorted transistors.
Plugging the monitor T1463 explodes (it is one of the burned transistors on the chassis)

see pag 1 on this manual
http://www.vernimark.com/arcade/archive/monitor/mon_rc_kt3_serviceinformation.pdf
it is related to the power management but I didn't any other check.

[PaulSwan]

Ideas:
 - Leave T1463 and U7470 out and verify that you have good smooth unregulated DC voltages out of the rectifier.
 - Leave T1463 out, insert U7470 and verify you have a square wave in line with the manual at the base of T1463.
Paul.

[vernimark]

Yes, I was thinking more or less the same.
yesterday I dedicated my time to the board. now I've a regular -5V (7905 was faulty) but the board doesn't work yet.
PCB has been repaired by someone used a wrong solder iron; a lot of tracks are broken and I'm doing what I can...

this is the status

[PaulSwan]

Just this week I've been working on adding Quasar to my little tester. In the next couple of weeks it should be finished.
If you have a Fluke, Macro in the UK has an adaptor for the Z80 to 2650 that can be used.
Paul.

[vernimark]

I don't have a Fluke, I absolutely have to buy one....

That board is a pin in the ass, I'm not sure I can repair it.

this is an example what I found...

[PaulSwan]

If it's beyond saving I can exchange it for a working in a couple of weeks.
Paul.

[vernimark]

Wow

In the meantime I couldn t resist and I Tried to tepair the board.
Looking at the auxiliary board z80 008/CA1 which is the Ic 13? It seems to be a 7404 but i m not sure.

And ic6 and 7?

[PaulSwan]

Likely components:
IC6 = 74LS04
IC6 & IC7 = 4016 or 4066

[vernimark]

Thank you.

I found some faulty ICs but I've still problems on the data bus. it seems that more signals are overlapped there and I changed all drivers that access on it. tonight I'll check all enabling signals. On the main CPU reset pin arrives a square wave.

[synonym9]

THen I took a spare transformer with secondary coils burned (11VAC used for +5V) and I opened this too. Then I removed the primary part from my original transformer and the secondary part from the other transformer.
I made a transfrankenstein (pay attention, not a transexual frankenstein)

THAT IS what I call amazing skills and great restoration!!! 

[vernimark]

Thank you... unfortunately I'm not so skilled for other issues. For instance I sent the board to Piero because I was going crazy with that!

This week I'll try to understand the monitor doesn't work...

[synonym9]

 There are probably no members restoring on that high level at every aspect.

I am like you, I am vrry good with tools. I can solder, weld, grind, work with a lathe and all that but suck at electronics....but rhere are people who can do it for is was better we ever could, and it is ok that way. 

[vernimark]

If you want you can If you have the patience you can learn a lot of things from this hobby...

Paul, I did what you said.

so on the rectifier board I have 320V instead of 300V bit I dunno how to regulate it because there is just a diode (that I changed but nothing changed) and a little transformer and few resistor used to produce other voltages (I suppose)

So going to the transistor T463 (BUW84)...

Collector: 320V instead of 290 (I don't know if this difference is in tolerance)
Base: I definitely don't have a square wave: https://www.youtube.com/watch?v=QdE8mGsMS8M

looking at the power regulator board I can say that this wave is generated by TDA2581Q. I haven't this TDA but I bought on ebay a couple of them. Once I receive it we can proceed

In the meantime if you have any idea how to step down the power from 320 to 300..... :O I'm scared the primary coil of the little transformer has some loops shorted...

[PaulSwan]

That's probably correct - the unregulated side is somewhat variable based on the mains input. e.g.
 240VAC == 339VDC
 220VAC == 311VDC
...so your starting voltage looks within range.
Paul.