[Boatanchors] REAR88 mods.

[Brian Goldsmith]

Joe wrote:-


>I'm working on a heavily modified AR-88 that I bought a few years ago.

****** G'day Joe,you should be so lucky!



 >I am trying to understand what some of these mods were designed to do and
where they came from.Some are basic, for example, the 5Y3 was replaced with
diodes and a new output transformer was added so an 8-ohm speaker could be
used.

*****  The new output transformer was probably not added so an 8 Ohm speaker
could be used.I'll bet the original burned out and a replacement was found
to be made of unobtainium,any old port in a storm etc.

 

>Some are weird. The audio output was changed from a 6K6 to a 6V6.


******** Quite common as the AR88LF used a 6V6.Also,a  replacement output
transformer would be much easier to match a 6V6.The change of tube meant a
change of grid bias and this was easily achieved by interchanging R44 (160
Ohm) and R43 (100 Ohm).


 Along the right edge of the set (in front of the power transformer), a 6SN7
and a 6K6 were added. I'm sure I'll find more as I probe further. The
workmanship is so good that it would be easy to confuse the mods with
factory work. This leads me to assume that the former owner knew what he was
doing.

****** A picture would be worth a thousand words.Looking from the front
panel along the top right edge,the original tube lineup was 6H6 (V8),6H6
(V9) and 6SQ7 (V10).
Are these tube types still there? 
 

>The set is gorgeous and works well with two weird problem: with AF Gain
wide open, it sounds great. If I back the AF Gain to a half-way position,
the set motorboats. Thus, I am leaving the audio gain fully open and am
using the RF gain as my volume control.


****** You will need to gut all of the original "bathtub" type multi section
paper capacitors and replace the innards with modern polyester types.


> The second odd-ball problem is that the radio has far more gain with the
Selectivity Switch in the No. 2 position. It should have more gain in the
No. 1 position.

****** The different gain from Sel 1 to Sel 2 is normal.In Sel 1 the IF
transformers have a double humped pass band,in Sel 2 etc the response is
peaked and has slightly more gain.


 >It motorboats with Selectivity set to the No. 3 or No. 4 positions.

Any insights and help would be appreciated. 



**** See above about gutting and restoring ALL the bypass caps.

I have taken the liberty of posting this to the original list and to the RCA
Equipment list where a number of 88 afficonados hang out.

Regards to all,Brian G.