Got tired of looking at my brother's broken guitar amp.
Its a Beltone AP-12 that someone lovingly pulled all the tubes out of, and broke one for dessert. I have boxes of old vacuum tubes that are a sad relic of my past; I figured I could find a replacement.
Its a 6AR5. Various sites refer to it as a "commen pentode" one going so far as to claim "This can often be seen in old thrown out televisions" .
I could have bought one for 10.00$ USD, which was more than I was willing to invest. I dug through my boxes.
I didn't have one. I searched for a replacement. The sites wern't real forthcoming on that issue, but by happy accident I found a schematic a Japenese fellow had posted for a receiver design, and he'd noted that I could replace the 6AR5 with a 6AQ5. I found 4 6AQ5s within ten minutes. The sites agreed the pinouts were identical, that the curves were close to matching - and most importantly, the replacement exceeded the performance of the original. I stuck the tube into the amp, doublechecked everything, and plugged it in.
Presently I found the loose wire between the power switch and the fuse. Clamped it by way of a jury rig, tried again. Amp lit up, tubes glowed, the speaker made that sound-not-sound , that peculiar clearing-of-throat
hum/not hum indicative of sucsess.
Now to solder it up, replace the wobbly power switch, and find myself a guitar.
Incidently, the amp contains the following tubes, from the side of the board which contains the transformer:
6AR5 6X4 6AV6 6AV6 6AV6
Which comes to 3 @ 6AV6, 1 @ 6AR5 and 1 @ 6X4 rectifier.
I am told the Beltone was actually made by Teisco. The plate on the back reads
Davis Importing Co. Ltd.
Musical Instrument Amplifier
Model No. AP AP-12
115 V. 60 CYC. 31 VA.

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