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I’m considering this Orange AD30 off a very good friend of mine, I’ve known the amp from when he got it 10-15 years ago and it’s had its fair share of issues.
Currently it’s working ok but he’s lost trust in it and wants to move it on.
It blew fuses fairly often so he ended up getting a new Mercury Magnetics power transformer and a full set of EL84s installed at the recommendation of local guru Guy Benfield, who said the AD30s are known to blow transformers. It continued to blow fuses unfortunately so took it back, got the recitifer tube replaced and fingers crossed it’s been ok since. Is it likely the output transformer will need replacing too? How do I tell if it’s on the way out?

Any amp techs know much about these amps or common issues?

Maybe have Steve (Bartlett) take a look at it?

FuzzMonkey wrote: ↑Tue Nov 14, 2023 6:20 pm Maybe have Steve (Bartlett) take a look at it?

That’s on my list this week probably.

Yeah replace the fuse with a nail

The AD30's were improved over time, that is an early model. For example I think the heaters were on the PCB in the early series, pretty sure they moved them to copper wires in later models. A good service and the Bias set correctly (cathode bias resistors may need replacing) should have it running reliably. The OT is likely to be fine.

See attached PDF for details.

sizzlingbadger wrote: ↑Wed Nov 15, 2023 9:13 am The AD30's were improved over time, that is an early model. For example I think the heaters were on the PCB in the early series, pretty sure they moved them to copper wires in later models. A good service and the Bias set correctly (cathode bias resistors may need replacing) should have it running reliably. The OT is likely to be fine.

See attached PDF for details.


AD30TC_testissue9.pdf

Thank you! I knew someone on here would most likely have some knowledge. Appreciate the info.

Forgot to say don't use the Standby switch, just leave it in the on position, thats what fucks the rectifier tube up in these amps.

Replacing a power transformer because an amp *occasionally* blows fuses seems a bit heavy handed - especially if the rectifier valve hasn’t been replaced first. I hope they didn’t have to pay for that, since it doesn’t sound like it fixed anything.

Some amps do use under-rated fuses. The surge when the standby is switched on causes them to blow, then the amp goes to a tech who can’t find anything wrong, they replace the fuse with the same value, then it blows again later on. It can be very frustrating for the owner!

While upping a fuse value is generally bad practice, it can sometimes be a simple solution to a problem amp that is otherwise checking out fine. It has to be done slightly and carefully though!

Always good practice to check the correct value of fuse to use, and whether it should be a slo-blo to cope with the initial spike. Never rely on what’s in there being correct.

RectifiedAmps wrote: ↑Thu Nov 16, 2023 8:09 pm Replacing a power transformer because an amp *occasionally* blows fuses seems a bit heavy handed - especially if the rectifier valve hasn’t been replaced first. I hope they didn’t have to pay for that, since it doesn’t sound like it fixed anything.

He paid a good amount to have the transformer fitted, and no nothing was ever acknowledged when it was taken back to get fixed a second time. These are some of the reasons my mates had a gutsful of the amp and lost interest and trust. But moving on, I’m now the one about to make an offer and trying to figure out the risk involved in doing such a thing. I figure if it’s unlikely to blow the output transformer there isn’t too many other expensive things to go wrong? A good service with the suggestions above by Sizzlingbadger might be enough.

It sounds like the rectifier was to blame. Like Sizzlingbadger says, it’s under stress from the poor standby switch design so it probably had an intermittent short. A simple fix for the standby is to wire a 47k/2W resistor across it, which allows the capacitors to charge up in standby, which avoids the big spike at switch-on.

The output transformer should be safe. They usually only get toasted by output valves shorting out and yours has new ones. If it had shorted turns from previous failures then it’d sound hummy and distorted in a bad way but it still wouldn’t cause a fuse to blow. The secondary power supply (HT or B+) is also fused on AD30s, which should protect the OT from valve shorts anyways.

Ok so had my first concerning issue crop up on the amp, hissing, squealing sound at end of this video.

As simple as a tube maybe?

https://youtu.be/1vjwpUCECtk?si=tndHA3TqaJxSErgr

Does it keep doing it or does it come n go? While it’s having the problem, fiddle with the controls and see what affects the noise. Then try switching channels and see if it’s still present. It sounds like a preamp issue - if so, turning down the master vol should reduce the noise too.

RectifiedAmps wrote: ↑Fri Nov 17, 2023 3:49 pm Does it keep doing it or does it come n go? While it’s having the problem, fiddle with the controls and see what affects the noise. Then try switching channels and see if it’s still present. It sounds like a preamp issue - if so, turning down the master vol should reduce the noise too.

As soon as I turned amp off and on again it went away, it was present on both channels and disappeared if I pulled the lead out. Noise reduced along with MV if turned down.
Didn’t check anything else, my next step will be to tap each tube with a pencil to see if I can get some squealing/ microphonics going again.

The two channels are totally independent from the input jack all the way through the preamp to after the master volume. So if the noise affects both channels but the master vol reduces it, my money would be on the input jack. There are no preamp tubes that are shared between the two channels so it couldn’t be a bad tube. Next time it happens give the guitar lead a wiggle in the input jack and see if anything changes.