[Boatanchors] Modified AR-88

[Carl]

Id start by replacing a few of the old bypass caps at a time starting at the 
audio end....unless it has already been recapped.

Carl


----- Original Message ----- 
From: "mac" <w7qho at aol.com>
To: "Joe Connor" <joeconnor53 at yahoo.com>
Cc: <boatanchors at mailman.qth.net>
Sent: Saturday, January 16, 2010 8:43 PM
Subject: Re: [Boatanchors] Modified AR-88


> Joe,
>
> My guess would be that a previous owner added a push-pull audio output
> stage using a pair of either 6V6s or 6K6s.  (No idea why you now see
> one of each.) The 6SN7 would be the phase inverter.  Motorboating
> usually means bad or too small decoupling caps in the B+ circuits.
>
> The AR-88 is reasonably roomy under the chassis.   Suggest you get an
> original  schematic and do a little reverse engineering to dope out
> just what  mods have been done.
>
> Dennis D. W7QHO
> Glendale, CA
>
>
>
> On Jan 16, 2010, at 3:58 PM, Joe Connor wrote:
>
>>
>> I'm working on a heavily modified AR-88 that I bought a few years
>> ago. 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.
>>
>> Some are weird. The audio output was changed from a 6K6 to a 6V6.
>> 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.
>>
>> 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. 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. It motorboats with Selectivity set to the No.
>> 3 or No. 4 positions.
>>
>> Any insights and help would be appreciated.
>>
>>                                Joe Connor
>>
>>
>>
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