04-08-2020, 06:14 PM
(This post was last modified: 04-08-2020, 06:16 PM by Mike Watterson.)
Thankfully the IF audio out is perfect. Those modules are not pleasant to remove.
The fading is ONLY straight after power on, ONLY if it's been off a while. Once it's going you can turn it off maybe for 10 minutes. Once it's going it's fine and has never then faded.
Next is to set up meters on all the likely points on the amplifier, there is maybe only just over a minute before it comes back, and then you'd want to leave it for an hour.
The Lockfits should click into the holes without the pins being bent. Clue in the name. The ends of the leads should not be bent over. The lockfits should be sitting straight and not bent or stressed.
Any of the soldered can transistors can grow whiskers if the inside has too much tin. I've a couple of sets with original AF117 transistors that are probably different production because they are fine. I'll leave AF117s alone if they are working today, because if they were going to grow whiskers they've had nearly 50 years to do it. I compared a Russian military part with a shorted AF117, I photographed the whiskers. Rarer on the OC171 or whatever similar part and on the VHF IF version. I'm sure it was a production issue, too much tin. The Russian part isn't a soldered can, more like the older top hats, but internally it looks more like a Silicon planar chip, though Germanium.
I put in 2 x BC547 (= BC107, BC147) which is simply a higher voltage part, maybe even by selection on the basis that the BC148 might fail eventually, being in something more suited to a BC108 etc. I think the Hackers are better made, but the PCB on my two Hackers weren't properly designed for a BC148 (which was dead). The other model had a BC108 and some other small differences, though the amps seem to be interchangeable on the RP25A and RP18. I forget which had the BC148.
The fading is ONLY straight after power on, ONLY if it's been off a while. Once it's going you can turn it off maybe for 10 minutes. Once it's going it's fine and has never then faded.
Next is to set up meters on all the likely points on the amplifier, there is maybe only just over a minute before it comes back, and then you'd want to leave it for an hour.
The Lockfits should click into the holes without the pins being bent. Clue in the name. The ends of the leads should not be bent over. The lockfits should be sitting straight and not bent or stressed.
Any of the soldered can transistors can grow whiskers if the inside has too much tin. I've a couple of sets with original AF117 transistors that are probably different production because they are fine. I'll leave AF117s alone if they are working today, because if they were going to grow whiskers they've had nearly 50 years to do it. I compared a Russian military part with a shorted AF117, I photographed the whiskers. Rarer on the OC171 or whatever similar part and on the VHF IF version. I'm sure it was a production issue, too much tin. The Russian part isn't a soldered can, more like the older top hats, but internally it looks more like a Silicon planar chip, though Germanium.
I put in 2 x BC547 (= BC107, BC147) which is simply a higher voltage part, maybe even by selection on the basis that the BC148 might fail eventually, being in something more suited to a BC108 etc. I think the Hackers are better made, but the PCB on my two Hackers weren't properly designed for a BC148 (which was dead). The other model had a BC108 and some other small differences, though the amps seem to be interchangeable on the RP25A and RP18. I forget which had the BC148.
