[ARC5] RCA AR-88 Problem

[Dennis Monticelli]

I would definitely suspect grounding.  All bolts, nuts and screws
associated with grounding should be loosened and re-tightened if you can
reach them.  If you can replace or add star washers on these fasteners, all
the better.

Dennis AE6C


On Tue, Jun 4, 2013 at 1:04 PM, Richard Knoppow <1oldlens1 at ix.netcom.com>wrote:

>     My AR-88 is a former Navy receiver so it may be on topic here. I've
> renewed this receiver as much as possible. Replaced all the bypass caps in
> it.  The bathtub caps were all leaking oil. They were replaced by modern
> film caps on terminal strips. I had no luck trying to restuff the original
> cans. I also replaced the Micamold paper caps in the RF compartment with
> film caps.  Everything works but I am getting regeneration on the top three
> bands. I think this is originating in the second RF stage. I have also
> recently had a problem with the plunger trimmers between the second RF and
> mixer going out of range on two bands.  I don't know if these are related.
>  Touching the second RF tube or mixer tube moves the points of oscillation
> around but does not get rid of them.  I've resoldered the ground
> connections to both tube sockets. The regeneration varies with RF gain as
> one would expect.  Its obvious that there is feedback but I can't figure
> out where its coming from.  I've tried bridging the new film caps in the RF
> with ceramic caps to no avail. Also tried different tubes.
>     I am about to see if the trimmers may not be grounding completely.
>  The chassis had a lot of junk on it partly from the leaking caps. The
> trimmers are held on with hex nuts at the top and there are solder tabs on
> the bottom against the chassis. Its possible they are not grounding all the
> way.
>     I have been posting on the RCA equipment list but am also posting here
> and on the boatanchor list to see if I can get a larger audience.  I need
> to hear from others who have restored AR-88's and might have encountered
> similar problems.
>
>
> --
> Richard Knoppow
> Los Angeles
> WB6KBL
> dickburk at ix.netcom.com
> ______________________________**______________________________**__
> ARC5 mailing list
> Home: http://mailman.qth.net/**mailman/listinfo/arc5<http://mailman.qth.net/mailman/listinfo/arc5>
> Help: http://mailman.qth.net/mmfaq.**htm<http://mailman.qth.net/mmfaq.htm>
> Post: mailto:ARC5 at mailman.qth.net
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>