HP 6050A (NOT Agilent) DC Load mainframe repair

[freelserg]

Hello everyone.
I"ve just got an HP 6050A (NOT Agilent) mainframe in not working condition.
It's a HD6303RP CPU based model.

It has no display after power ON but FANs are running in some manner.

Downloaded right service manual - 9018-03848.pdf
All power rails are good - +5V and +13V

Found bad PNP Q201 - it generates PCLR* signal for CPU at power on sequence.
After replacing it there was no success - still get no display.

Ok. Let's read Service Manual again.
It says:

"The selftest is performed by the primary microprocessor (U203) and starts when the primary clear ( PCLR* ) signal goes
false (High). First, the RAM, ROM, and the microprocessor's internal timer selftests are performed. If any of these tests
fail, the front panel display will probably remain blank. The failure can be detected by measuring a square wave on the
SA_GATE line at TP201-8 (see Figure 3-2). The type of failure is indicated as follows:
10Hz square wave--indicates a RAM failure
100Hz square wave--indicates a ROM failure
1KHz square wave--indicates a internal timer failure
Square waves will not have a 50% duty cycle. It is also possible for a selftest failure to ''lock-up" the microprocessor and
cause a blank front panel display and no error square wave to appear on the SA_GATE line. If ''lock-up'' occurs, try to
isolate the problem by performing the Primary Signature Analysis Tests or by replacing U203."

Got it!
Checking on the SA_GATE line at TP201-8 shows something like ~2Hz square - strange thing...

Ok.
I've ordered another CPU HD6303RP because it's cheaper than obtain Signature Analyzer.
CPU is not arrived yet but my concern is what if it is has a bad ROM?

Is it real to get ROM dump from any working mainframe?
Is there anybody encountered the same issue?

Thanks for replies.

[m k]

Did you use spare Q201 part?
(13-14-15)
Maybe the whole network is bad.

[freelserg]

Hi.
Actually i used a part of Q201 network.
I've tested it and it seems to be ok (except those for PCLR* signal).

2days ago i received a new CPU and replaced the old one.
The dead old CPU was the cause.

So now it's all working.

Thanks for answer.