VOX AC30 Transistor Crackling

Рет қаралды 2,758

Stuart ukguitarampguy

7 ай бұрын

Looks like a classic old valve AC30? Hmm... think again!

Пікірлер: 50

@alexdeleon7135 7 ай бұрын

Great result from the most simple testing method. I love it when things zip along. Not only did you correct the issue, you performed preventive maintenance on the second IC. This additional action is not only added value, but is an affirmation of your selfless concern for any future expense to the owner. You are an amazing person, Stuart. I surmise that the units taking up space on the bench will provide ample episodes to come. Well done. Cheers!

@stuartukguitarampguy5830 7 ай бұрын

Cheers Alex you are very kind!

@edwardhannigan6324 7 ай бұрын

Great job Stuart, another lucky one..Saves the client dosh and just before Xmas...! Like the way you found the fault, always something new to learn from you....Ed..uk..😄

@katherinemacdonald9909 7 ай бұрын

Craig Macdonald here great to see you find this fault , can stop following your repairs by the way I changed the two caps on the transistor fender stage 100 , and sorted great deep tone rich and load with no buzzing , thanks to you fixed for £ 14.00 including postage many thanks without your videos I’d never of known how to find it .

@stuartukguitarampguy5830 7 ай бұрын

Nice one! Well done.

@fiddlix 7 ай бұрын

Sometimes a waggle with an insulated tip is the best diagnostic tool we have. Excellent easy repair…Cheers from the US Stuart..!

@stuartukguitarampguy5830 7 ай бұрын

Thanks!

@electrolytics 7 ай бұрын

Thanks Mr. Stuart. Yeah that's a nice little beater for someone to knock around with. Kind of reminds me of an old Vox Cambridge amp I bought here in the US one time.

@montygore1200 7 ай бұрын

Good one Stuart. Thank you

@stuartukguitarampguy5830 7 ай бұрын

Cheers Monty.

@5barkerstreet 7 ай бұрын

great show Suart.

@stuartukguitarampguy5830 7 ай бұрын

Thanks!

@bluesplayer59 7 ай бұрын

Splendid 🎉

@ferraridinoman 7 ай бұрын

Nice one Young Stuart as always! Yep, a little corrosion and problems follow!

@stuartukguitarampguy5830 7 ай бұрын

Thanks!

@vintageguitaramp_guitarteacher 7 ай бұрын

Hello Stuart. Nice easy fix on that one. I have had one of the Birch Stolec Vox AX30s in for a quote. Valves but on a PC board and it's been messed about with. It won't be an easy fix. Never seen inside a solid state one before. Take care.

@stuartukguitarampguy5830 7 ай бұрын

Yes it was a new one for me too. Good luck with yours.

@michaelevans3852 7 ай бұрын

I'm happy to see a ss Vox on your bench. I recently helped a friend with his AC30S1. That amp is a tube amp, but I believe it is also digital as well. Maybe the preamp tubes just sweeten the sound. It does seem that Vox has made many versions of this amp. The one I recently saw was made in China. It did have a good sound but was made with many plastic parts. I don't think I'll be buying one any time soon. Once again, it is good to glean from your expertise.

@stuartukguitarampguy5830 7 ай бұрын

Thanks Michael.

@danielsaturnino5715 7 ай бұрын

Probably misture being closest to the input jack. Well done

@goodun2974 7 ай бұрын

Congrats, Vox, you've managed to transplant the high noise floor and rushing water sound of an unserviced vintage tube amp into a solid-state circuit! PS, looks like that blue filter cap was previously replaced by someone with lousy soldering skills.....

@stuartukguitarampguy5830 7 ай бұрын

Yes that cap had definitely been 'tacked in'!

@pda49184 7 ай бұрын

Well diagnosed and spotted Stuart. I once heard a hi-fi tech describe the issue you found as 'black leg' syndrome. That fairly concurs with what you found . Corrosion in other words. That amp looks very much like Birch-Stolec Industries model from the 1970. The company bought Vox and manufactured them in the Hastings area. Just one of the many owners of this brand you elude too.

@stuartukguitarampguy5830 7 ай бұрын

Thanks Pete. You have to really know your VOX history to know that. They've been through SO many iterations.

@goodun2974 7 ай бұрын

@@stuartukguitarampguy5830, There's a book about Vox amps, written by a British guy named Stephan Grosvenor, which goes into the technical aspects, circuitry, repair and mods/upgrades of all Vox amps. It's chock full of his own diagrams and drawings.

@stuartukguitarampguy5830 7 ай бұрын

Thanks. Do you happen to know the name of it?

@pda49184 7 ай бұрын

@@stuartukguitarampguy5830 Here's a paragraph from the VOX history page ; " Birch-Stolec Industries purchased Vox from Corinthian Securities in 1970 and moved the manufacturing facilities from Erith, Kent to Hastings, East Sussex. The "VSL" name was retained. Birch Stolec owned Lemark Transformers, a major Vox creditor from the VSEL bankruptcy. The V100 head, a 100 watt, all tube, printed circuit amplifier was introduced by Birch-Stolec as were the first printed board versions of the AC-30 and AC-50. They also produced slightly revised versions of the solid state Vox amps introduced by JMI in 1967. Rick Huxley, former bassist for the Dave Clark Five, became sales manager." So it seems that the concept of a solid state VOX AC 30 was a JMI idea from 1967, although I believe that model had the brown grill cloth as per the valve AC-30. The original range of VOX solid state amps were named ; Traveller, Virtuoso, Conqueror & Defiant, Supreme plus a range of bass guitar amps.

@ralphj4012 7 ай бұрын

@@stuartukguitarampguy5830 Possibly thevoxac30guide (site).

@brianmac8260 7 ай бұрын

That's OK, just stick an ART Tube Pre in front of it. 😆

@stuartukguitarampguy5830 7 ай бұрын

That would work!

@silasfatchett7380 7 ай бұрын

I've fixed amps by easing ICs partway out of their socket and pushing them back in.

@goodun2974 7 ай бұрын

If the sockets grip snugly and the legs of the IC's aren't too badly tarnished , the oxidation should wipe off of the pins when you reinsert the device. Still, I usually prefer to pull the chip out and clean the pins manually with a pencil eraser or fiberglas scratch-brush.

@stuartukguitarampguy5830 7 ай бұрын

Probably best to clean properly since you are in there anway.

@waynegram8907 7 ай бұрын

What was causing the Transistor Crackling issue? because the IC chips pins and socket needed to be cleaned?

@stuartukguitarampguy5830 7 ай бұрын

Yes bad contact between some of the IC pins and the socket. It was very corroded.

@matthewf1979 7 ай бұрын

Yeah, they’re not a ‘62 AC30 with Celestion Blues,but they’re still cool amps. You can do much worse for a vintage SS amp. Socketed IC’s sure are nice for maintenance, but my god do they cause problems after a few decades. All of the vintage computer channels must go through gallons of DeOxit collectively.

@goodun2974 7 ай бұрын

In my 45+ years of electronics repair, I've never had to replace an IC socket on an audio amplifier, FM tuner or the like; it's clear that the problem in this case was the badly oxidized, blackened pins on the IC itself (oxidized silver plating?) Cleaning the pins with a pencil eraser or fiberglas-bristle "scratch brush" is a better remedy than merely spraying with Deoxit, and I would caution against leaving Deoxit residue in the socket. An alcohol flush afterwards is recommended.

@stuartukguitarampguy5830 7 ай бұрын

Yes that's exactly what I did,

@ferraridinoman 7 ай бұрын

Yep! an alcohol flush always works for me!! HIC!!!!@@goodun2974

@stevehead365 7 ай бұрын

Household ammonia is pretty good at cleaning tarnished silver and clearing out the nasal passages should you feel so inclined.

@stuartukguitarampguy5830 7 ай бұрын

How do you think I get through the day? :)

@themrtomward 7 ай бұрын

Sorry to sneak in on this video but can you tell us about the “frying bacon” sound and how to be rid of it? This on my Fender 75 amp which can play sans bacon and sounds otherwise glorious!