Little bit of AR2 Help Please

tb lilley

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I've just repaired a spare AR2 which was giving me a too high reading on the +5VDC. All now appears to be well, and I'm now getting a nice steady reading of the +5 at the appropriate test point on the AR2.

Hooked up to the PCB (Missile Command) and the +5 has gone AWOL, but still reads fine on the AR board.

I don't think I've got a continuity problem as when I put my other working AR2 back in, the +5 reappears on the MC PCB.

So, I'm thinking I have a problem with connector J7 on the AR2, which should output the +5. As a first step I want to probe J7 to see whether the +5 is present and correct.

Question: which pins on J7 should I probe? The schem shows pins 5&6 as both having +5VDC REG, so is it simply a case of checking these? Is so, which pin takes black/red leads off the DMM. Excuse my ignorance, but my experience on DC voltages to date has been checking for voltages at a clearly defined test lug and ground point.
 
Argh!!

Replaced the 3055 but has made zero difference.

I've been all round the houses on this one. So far have replaced the 3055, TIP32, and resistors at R29 and R30.

The initial problem was a reading of about 12VDC on the 5. Replaced the 3055 a couple of weeks ago. No change. A week later replaced the TIP32. No change. Tonight replaced resistors at R29 and R30. Now reads +5 until PCB hooked up. Then voltage all but disappears. Replaced 3055 again. Problem remains.

So ..... I think the plan now is to replace all of the above in one go, plus the protection diode which I have so far left alone.

Which is the protection diode, is it the one at CR1 or at CR4? I'm only asking for future reference as both CR1 and CR4 are on the 5VDC line so I'll do both anyway.

CR1/4 is listed as "50V 2.5A Miniature Axial Lead High Current Rectifier". Is there something else I can ask for that the morons down at Maplin (UK equivalent of your RadioShack) might recognize?

I'd like to get this working, not that I'm in a desperate hurry for it, but I would like to be able to be confident in future doing AR repairs. Cheers.
 
Which is the protection diode, is it the one at CR1 or at CR4? I'm only asking for future reference as both CR1 and CR4 are on the 5VDC line so I'll do both anyway.

CR1/4 is listed as "50V 2.5A Miniature Axial Lead High Current Rectifier". Is there something else I can ask for that the morons down at Maplin (UK equivalent of your RadioShack) might recognize?

I'd like to get this working, not that I'm in a desperate hurry for it, but I would like to be able to be confident in future doing AR repairs. Cheers.

CR4. I use a 1N5059 (A14F Cross GP Rectifier) in the kits I sell, but you can also get away with a 1N4001. It sounds like the only thing you haven't yet replaced is the LM309.
 
Thanks - I'll drop by my local old school electronics shop on the way home tonight - the old boys in there know their stuff and seem to stock most parts.

Yes - if this plan doesn't work then it'll have to be the LM309 next. 8 legs on that .... which is why I've tried to exhaust every other possibility first !
 
BTW I have a couple of AR-II's rebuilt and bench-tested, ready to go for $35. Just wanted to put that out there. :)

(Billy, I do have one AR-II -02 set aside for you as well. :))
 
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