AMI Jukebox repair – 1958 AMI 200 Jukebox

AMI jukebox repair

Another first for Keld Ampworks – the first AMI Jukebox repair. I’ve turned down jukebox repairs in the past because I naively had visions of a 7 foot unit arriving in my rather small workshop! This customer was quick to clarify that the amp unit itself is quite small and transportable from his Lincoln location. Nonetheless he sent me some pics of the full unit (above).

AMI jukebox repairIt is a US unit, bearing original battle scars and running on 110V through a transformer.

It was exhibiting a loud hum and excessive breakup. The customer asked me to do a basic valve test and check over and then report back.

It runs a preamp with one 12AU7 and one 12AX7, then a 12AU7 cathodyne phase inverter and a cathode biased 6L6 pair. One 12AU7 tested faulty (replaced with a valve from the customer’s collection), but the main problem was down to the badly worn 6L6 pair (replaced with a brand new matched pair of Russian EHX valves).AMI jukebox repair

US amp manufacturers in the ‘old days’ didn’t tend to Earth their amps. All amps that leave my shop should have correct earth, fusing and safety practice so I fitted an external earth to this unit. Since the unit goes inside another unit this was fitted with a flying lead and solder tag to screw to the main chassis.

This is a favourite toy of the customer’s grandchildren and I’ve since heard that they’ve given it a thorough testing!

If you need an AMI jukebox repair, please get in touch.

Mesa Boogie Bass amp Repair

Mesa Boogie Bass 400+ Repair

This mesa boogie bass amp repair had the highest power valve count I’ve seen. The amp uses no less than twelve 5881 6L6 valves!

Like the recent fender amp repair this valve amp was blowing fuses. Also like the fender repair, the failure was down to a damaged power tube. Two in fact.

Much is made of Mesa Boogie’s insistence upon the use of mesa branded valves on guitar forums and these guys come in for quite a lot of stick. You can read Randall Smith’s defence of the idea here. My opinion is that the principle is reasonable for the majority of non technical users.

In this case, the amp had been fitted with Sovtek valves. Aside from the two failures many of the valves no longer matched well.

By testing mesa boogie valves in my valve tester I know what non mesa valves are within mesa parameters for use in their amps. I could tell that 4 of the sovteks were out of spec, meaning that 6 of the 12 needed replacing. After completing this simple task the amp was fixed.

If you have a mesa boogie bass amp repair please contact me via the contact page.