[Hallicrafters] R-45/ARR-7 Questions

[Mike Everette]

Regarding the value of the bypass caps, they may not be 0.0082 uf.  Be careful of how you read the color code, because there are several versions of the six-dot code and I'm suspicious that there may be another non-standard version.  A long time ago I made a similar mistake in an SCR-522 VHF receiver and put in bypass caps which were too low in value; the IF strip oscillated as a result.  Wish I could remember the exact details but they escape me.  The error was a direct result of misreading the color code.  At that point in the project I had no manual, only a schematic with symbols only, no part values.  When I found a manual and parts list, the problem became very clear.

This SCR-522 had been plagued with numerous "exploding" postage-stamp caps, which literally blew apart when they shorted out; and yes, I was running the correct B plus into it.

The ARR-7 manual is on BAMA, if you need it.

73

Mike
W4DSE

--- On Sat, 3/24/12, Joe Connor <joeconnor53 at yahoo.com> wrote:

> From: Joe Connor <joeconnor53 at yahoo.com>
> Subject: [Hallicrafters] R-45/ARR-7 Questions
> To: "hallicrafters at mailman.qth.net" <hallicrafters at mailman.qth.net>, "milsurplus at mailman.qth.net" <milsurplus at mailman.qth.net>
> Date: Saturday, March 24, 2012, 10:08 PM
> I just picked up a pretty nice
> R-45/ARR-7 (the airborne SX-28). It came with the PP-32
> power supply. Thankfully, a prior owner replaced the power
> xformer so the set can operate on 60 cycle power. With a
> little tinkering, the set now works pretty well. 
>  
> I have some questions that I hope you can answer:
>  
> 1. From what I've read, it's a good idea to bypass V-12
> (6AB7), the radiation suppression tube. How do I go about
> bypassing it?
>  
> 2. Interestingly, most of the bypass caps are .0082 mfd, not
> .01 mfd. Are these mica caps or paper caps? If they're mica,
> I'll probably leave them alone. 
>  
> 3. The audio output (6V6) and 1st audio (6SQ7) each have a
> 20 mfd bypass cap. I'll be damned if I can find them. Does
> anyone know where they are located.
>  
> 4. I know this is probably a needle in the haystack, but
> might anyone have a front-panel cover for the scanning
> mechanism?
>  
> 5. Is there anything else that I should watch out for?
>  
> With this set, I got some paperwork that shows how good we
> have it today with the Internet. The fellow who owned this
> set in the '60s apparently tried desperately to find a
> manual for it. I have the letters that Hallicrafters and the
> ARRL wrote to him politely stating that they couldn't help.
> Now, we click on Bama and there's a manual on our computer
> screen. It's pretty amazing, when you step back and think
> about it.
>  
> As always, thank you for your help.
>  
>                                        
> Joe Connor
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