Managed to get a dead DVP-1 powering up. Two A1175 on the +5V power supply on PSU. Unit powers up, but hangs with an ‘A’ on display. Service manual for all it\s worth says CPU and or RAM. CPU seems to be ticking over in that it’s receiving signals. Not sure what to do. Any advice warmly appreciated.
Best wishes, Craig
Probably worth buying a replacement RAM chip to see if this fixes it.
They’re quite cheap.
another method to fix here
Thanks for suggestions. I bought a Gq4x4 eprom blower and will burn a new eprom with the OS. I’ll keep you posted as to how I get on.
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Tested old EPROM in Gq4x4 and it tested fine. Blew a new EPROM all the same and tried both. Still no boot. As I mentioned the CPU appears to be running in that Xtal is fine and pins are pulsing or high or low. I’m kind of stuck as to what to do. The reset circuit seems to be functioning.
One thing I noticed is the dual wound transformer is only outputting 4.7V on what should be the 5V winding. This was mesured with no load at all. Would it matter that the 5V is actually 4.7V ?
AC 4,7V from 2-nd coil of transformator - it’s pooor!
And taking into account measurements at idle - this is also incorrect, since the voltage drop on the transformer winding and the transition resistance on transistors Q1-4 & diod-bridge DB1-2 will be added, first test it in working condition and then check the DC power supply according to the service manual
I’ll sub in a new 5 volt AC source and see what happens. Thank you.
Judging by your reasoning, you haven’t looked at or studied the SM, where it is noted that the power supply has several secondary voltage lines (2 DC 5V lines; 2 DC 15V lines including a 3-pole power supply and an power line for the +18V). Without understanding the peripherals and the condition of the power supplys, you will ruin your DVP completely…
So, help and advice are pointless… Goodluck!
Hi, Thanks for the concern. I undestand the PSU…I had to fix it before I got as far as I am with this repair - all the DC power regulators now work and I replaced two dead A1175 transistors on the 5V DC rail. What I was referring to and i’m sorry I didn’t make it clear was disconnecting the 5V transformer secondary from the PSU board and connecting a stable external 5V AC source. Would this be an OK to proceed in your opinion?