Repairs to the Peavey Classic 50 in Australia

Classic 50 P1020263Welcome back to the blog, everyone. We have been servicing the Peavey Classic Series 30 watt and 50 watt combo’s since their introduction back in the 1990’s and we are in fact still the A.M.I. authorised Peavey warranty repairer (valve/tube amps only) for NSW. Since the 1990’s the 30 watt 1×12 combo has overtaken the 50 watt models in terms of popularity as they provide reasonable performance in a compact package. Reliability has been questionable at times – we have had to repair printed circuit boards (PCB’s), replace transformers, valves and 9-pin valve sockets, and so on. Bias for the EL84 output valves is non-adjustable, which means some amps run rather hot.

Classic 50 P1020262The subject of this blog is a more recent 2×12 model delivered to us by a local music shop, reported as losing output and nil reverb level. It may not be immediately obvious from the photo, but the speaker connection tagstrip, normally pop-riveted to the speaker basket, has come adrift, causing unreliable operation. This is a problem we have witnessed many times with the cheaper OEM speakers supplied by Eminence of the USA to various amp manufacturers. The only reliable solution is to carefully drill out the remaining body of the pop-rivet and refasten the tagstrip by other means.

Classic 50 P1020264In the meantime we isolated the ‘nil reverb’ problem to the reverb tank itself, which is mounted in a vinyl bag at the bottom of the cab. The only way to gain unrestricted access to both the problem speaker and the non-functional reverb tank is to remove the speaker baffle completely from the cab. This is what is known as a ‘floating baffle’, with mounting screws along the top and bottom front of the cab, which must be removed. The amp chassis has to be removed before this can happen, of course.

Classic 50 P1020267Once the baffle is removed and placed face down on the workbench, we can repair the speaker. We choose to refasten the tagstrip with nut/bolt/lockwasher rather than another pop-rivet. It takes longer but will survive the demands of rock’n’roll guitar. The other speaker on this 2×12 baffle is checked OK.

Classic 50 P1020269Before we re-install the baffle into the cab, we will repair the reverb tank. One of the transducers tests open-circuit (O/C) and is not repairable, so we will replace the unit altogether. This is not a bad thing as we will upgrade the reverb with one of the ‘MOD’ tanks, The reverb will sound much better than it did previously.

Classic 50 P1020270Reverb tanks are available in various combinations of impedances and delay times, so it is important to select the correct unit for the individual amp. In the Peavey Classic Series, the reverb tank is driven by an IC, requiring a different input impedance than for example a Fender ‘Deluxe Reverb’. The replacement tank is placed within the vinyl bag, which provides some degree of isolation from vibration, which in turn is screwed into the bottom of the cab. The baffle and amp chassis are each reinstalled into the cab, and the reverb cable reconnected within the amp.

Classic 50 P1020272We had previously tested all the valves (tubes), external to the amp, and also carried out a power output test and electrical safety test. The final play test revealed a huge improvement, and the amp was returned to the music shop. Thanks for checking out the blog and we are located here in Gosford (Wyoming) NSW for all your valve (tube) amp service needs, including custom design. IR.

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