Roland Bolt-60

[laurie]

Picked this up as scrap. Not working, bottom of the cabinet smashed and poorly repaired.
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Bolt-60_1.jpg (344.51 KiB) Viewed 23018 times

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Bolt-60_3.jpg (194.5 KiB) Viewed 23018 times

[Pepe]

Interesting, I have never seen this amp series. When have they been made?

[laurie]

So what was wrong with it...

• All the tubes had failed. Output tubes (6L6GC) were both faulty. Almost no gain. The 12AT7 phase inverter was crackling. All replaced.

• HV caps had failed. Replaced.

• The 1500 Ohm grid resistors were both reading low. Replaced.

• Some of the low voltage electrolytics were puffy and some were actually leaking. Replaced all caps.

• And the main reason it wasn't working - a dry joint on one of the interstage coupling caps. No sound getting out of the preamp to the power amp.

• All the potentiometers were crackly and intermittent. Cleaned and lubricated.

• The amp had been dropped. Hard. The bottom chipboard was broken and a really poorly implemented brace had been screwed in with deck screws. Repairs are in progress. Pics to follow.

• One of the power transformer bolts had snapped off, presumably when it was dropped. Replaced.

• One of the speaker mounting bolts had pulled out of the chipboard, presumably when it was dropped. Repaired. Luckily the speaker appears to be OK.

• Both reverb tank cables had been hit and were almost cut through, so reverb was flakey. Replaced the cables.

It now works as it should. These amps aren't worth very much, but it IS a Roland and has some mojo.
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Bolt-60_4.jpg (194.65 KiB) Viewed 23015 times

[laurie]

Interesting, I have never seen this amp series. When have they been made?

This one decodes to 1981. This is the only series of tube amps ever made by Roland - the Bolt-30, Bolt-60 and Bolt-100. Made from 1979 to 1984.

The phase splitter and output stage are identical to the AA864 Fender Vibrolux, minus the adjustable bias.

[BearBoy]

Cool find and another great repair job!

Had never come across this range before.

[laurie]

Cool find and another great repair job!

Had never come across this range before.

Completely new for me too.

I've replaced the destroyed rear brace with hardwood using some biscuits to locate and strengthen the joint, and added a plywood veneer to the smashed cabinet bottom. Fortunately the tolex on the bottom wasn't damaged so with the plywood strengthening the bottom it will look and feel like new after a coat of flat black.

I have some old rescued tolex from a Marshall cabinet that is a good match for the tolex on the amp and I'll use that to cover the new rear brace once the glue is dry.
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[Pepe]

Ah, neat!

[laurie]

Woodwork complete.
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Bolt-60_7.jpg (301.97 KiB) Viewed 22943 times

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Bolt-60_8.jpg (261.41 KiB) Viewed 22943 times

[laurie]

Painted and ready for tolex repairs.
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Bolt-60_6.jpg (356.15 KiB) Viewed 22943 times

[laurie]

And one last issue (gotta love these old tube amps). The top of the cabinet is detaching from the sides.

Either remove all the tolex and recover it - losing a lot of the vintage feel - or install internal braces.

Braces it shall be - aluminium angle epoxied and screwed into the top inside corners.