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Thursday, September 24, 2020

Global Specialties Corporation 6000 Frequency Counter -- Anyone have a Plessey SP8630B Chip?

Continuing my effort to improve my workbench and its test gear, this week I turned to an old frequency counter that I picked up at the Kempton Park Radio Rally in London many years ago. It was not working when I got it, but long-time SolderSmoke listeners will recall the tale of woe that resulted from my having soldered a replacement IC (that Tony Fishpool G4WIF had sent me) UPSIDE down.  Tough times my friends,  tough times. 

Well,  I'm working on it again.  First I converted it from 220 to 110 power.  I had a transformer in the junk box that fit nicely, both electrically and mechanically.  In the course of doing this, I learned something about this counter that I did not know:   As long as it is plugged in, even if you turn it off, the time-base oscillator keeps running.  And get this Color Burst Liberation Army members:  The oscillator runs at 3.579545 MHz.  TRGHS.    

With sunspots scarce and with Pete pessimistic about the solar cycle, VHF and UHF now seem more interesting.  I need to have more test gear for the higher frequencies.  This counter works up to 650 MHz.  Yea! 

When I first fixed this thing, I was quite pleased to get it going with "Input A -- 5 Hz to 100 MHz."  But now I want to get "Input B -- 40 MHz to 650 MHz" working also. I used a 50 MHz signal from my newly repaired HP-8640B to trouble shoot Input B.  I think one of the divider chips is bad.  It is a Plessey SP 8630B.   Does anyone have one of these chips in their junk box?  


  1. Available from a reasonably good supplier on ebay https://www.ebay.co.uk/itm/202315641935

    However the pricing is a mugging. Or is it? The IC probably cost more when it was new.

  2. Hi Bill,
    another ebay source (well hidden, but from KY this time): 381676125585
    Maybe OM Jeff WA#ZKR can help out.
    73s Joh

  3. The ebay.uk is pricey and I doubt the chip was that much new. You may be able to look at the schematic and find a similar ECL chip that you can substitute with not too much effort if other potential sources cannot help.

  4. You mentioned going to a qrp gathering in the last podcast, but, looking at the ARRL/TAPR Convention mentioned, did you know that a group with a similar name has a 9600 baud modem project TNC ? Its really affordable and cool. About $30 for everything! You get the board from "tarpn" which is actually Terrestrial Amateur Radio Packet Network , plus the microprocessor pre programmed. Then you order the rest of the parts with a shopping cart macro, and believe me, even though it seems like it won't work, it does, at DIGI-KEY ! Something like 22 dollars more. FOLLOW THE EXCELLENT INSTRUCTIONS, don't think you can fly through it without at least seeing the tips in the instructions, it will save you a ton of time. If everyone were to switch to 9600 with APRS and Packet, I'm sure there would be a revival. Check it out , took you right to the meat of the project, the ordering and assembly page. http://tarpn.net/t/nino-tnc/n9600a/n9600a2/n9600a2-assembly.html


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