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Yes, I noticed your initials on it – I think you were the one with the best diagrammatic skills, unlike my scrappy scribblings ? JW Sent: Monday, April 15, 2024 10:06 PM To: [email protected]

Was this fault found and fixed Graham? Would be interested what it was. Cheers, Martin G4NCE

Nice find Jon. I drew that schematic ?. -- Mike G8GYW

A fine little radio! And it fits the Low band SMT cougar amp! Robin G?GNE

HI Julian-much appreciated, Best regards. Jeff

Hi Chris, You may find the attached helpful – it shows the Tx RF circuitry of the pre-production B model (which was pretty close to the final from what I recall). I worked on quite a bit of the RF

Hello chris I think my friend have complete factory documentation for PRM 4720A from our army. wrote:

Hi Chris I was one of the engineers who worked on the design of this radio but it was so long ago I cannot remember details of the schematic. You could try contacting Jon Withers who posted earlier in

Hi guys.? So I did get that PRM-4720A radio, but sadly, is partly faulty. So the radio powers up fine, the RX is ok, but it has no TX signal whatsoever, no RF output power. What I am really after now

Hi Geoff - I think we have some of these new and boxed in our stores. I’ll check on Monday and let you know. Best regards, Julian Barnard.

HI Guys, Still looking for the above item to buy or maybe swap Jeff? G8XXI

2N4392 would be a reasonable sub, yes. --scott

one person said theirs was subsituted with a 2N4392 p

If the gain is in the correct ballpark and the breakdown voltage is high enough, the J112 will probably work, but the J112 is a much higher end part. --scott

Depending where you are, I bought 5 from Canada off eBay for $1, with about $6 shipping. 73 - Dan ac6ao / g3ncr

Thanks Shaun. Unfortunately their min order and shipping charge make it not viable!

Yes its just a switching/chopper. Thinking about trying a J112.

Here are a couple of sources, both reasonable: https://electols.com/shopping/en/transistors/34978-tis74.html ( https://electols.com/shopping/en/transistors/34978-tis74.html ) (Europe)

NTE467 should be fine. 2N4391, 2N5555 might be okay. Lead configurations may vary. JFETs are becoming rarer and rarer on the ground today, but this is likely just being used for switching. --scott

This might seem like an obvious question but I want to be sure that I use a correct substitution. On the A6A2 Microprocessor board Q6 is a TIS74. This appears to have failed. TIS74's are rather dated