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Author Topic: collins/Rockwell 851-S receiver problems.  (Read 793 times)
ZL1BDA
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Posts: 41




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« on: November 09, 2017, 08:03:41 PM »

Just picked up one of these rack units at a ham sale last week. Gradually getting it going, but, of course I do not have any extender boards for it, so signal tracing can be a problem. At present the RX fault LED is always on. When the manual tune switch is depressed I get audio, the RF gain control is effective and of course my frequency display seems fine, operating exactly as expected. Has anyone had experience with these units? It looks like a great general coverage receiver for my shack! BTW I understand that the USAF used them as HF receivers, so someone may have come across them in the service.
Hope someone has got some better knowledge than I.
73 Cliff.
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ZL1BDA
Member

Posts: 41




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« Reply #1 on: November 20, 2017, 03:03:25 PM »

Just picked up one of these rack units at a ham sale last week. Gradually getting it going, but, of course I do not have any extender boards for it, so signal tracing can be a problem. At present the RX fault LED is always on. When the manual tune switch is depressed I get audio, the RF gain control is effective and of course my frequency display seems fine, operating exactly as expected. Has anyone had experience with these units? It looks like a great general coverage receiver for my shack! BTW I understand that the USAF used them as HF receivers, so someone may have come across them in the service.
Hope someone has got some better knowledge than I.
73 Cliff.

Well I have got a bit more done. It seems that what I need is a 130 way extender card. The smaller 50 odd pin extenders are available, but the control system uses the "biggie". It is VERY difficult to fault find otherwise as the boards are all fully enclosed in a screening box. Has anyone come across these?
Otherwise it looks like a good source of mechanical 450 kHz filters and not much else.
ZL1BDA.
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ZL1BDA
Member

Posts: 41




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« Reply #2 on: December 05, 2017, 02:27:32 PM »

Another update. And now I am perhaps getting closer to the problem. The "Receiver fault" LED goes out when the "Synth Fault" signal on Pin 49 of the control board is grounded. Thus the fault must be in the synthesiser control system. The LED frequency all operates correctly, retain its setting when the system is switched off and acting very normally.
My BIG problem now is locating the source of the "Synth Fault" signal. I have already spent a couple of hours poring over my manuals, but have yet to locate it. What a pity Collins did not see fit to publish the equivalent of a "motherboard" diagram showing all the inter board connections!
So once again. Anyone got any ideas that might save ma a lot of time.
BTW I just finished restoring an HRO 500. Goes remarkably well for an old timer, it is now en route to a new home south of here.
Cliff Wright.
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