Re: RCA AR88D Comms Receiver.
Have you tried a 6J5G or GT rather than a metal type John?
I had a similar problem to yours with a DST100. This used a glass 6J5 with a metal can so I tried the all metal valve and it stopped oscillating like yours.
I also had trouble with my RA17. The EF91 oscillator cut out mid-band and I had to try others until one worked OK but the original was just slightly down on emission.
A third instance was in an R1132. This turned out to be bad earthing but VHF oscillators are more prone to this but... the AR88 tuning condenser might have a dirty contact forcing the RF current to adopt a different path. If you use switch cleaner do not get it between the vanes.
Finally there's always an option to use switch cleaner on the wavechange switch which might be resistive.
Padders are a good candidate to blame but I must say I've never come across a bad one.
Can you alter the HT to see if higher or lower voltage improves or makes matters worse.
Also.. can you measure the LT voltage with an RMS meter at the 6J5 pins in case this is low which will reduce emission and gain?
Allan G3PIY
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