CHAMP ELECTRONICS -" THE VALVE AMP HOSPITAL"

NOTTINGHAM, ENGLAND

 

SORTING-OUT THE "WORST VOX AC30 IN THE WORLD"

 

 

Two pictures of the AC30, as received!

 

 

Well, what can I say, Iíve seen many bad amps in my time but I think this Vox has to hold the title of the "worst amp in the world!!" Well certainly as far as Vox amps go anyway.

It was brought to me by a nice gentleman, Tim, who also brought me an Impact Head, together with the story of how heíd bought this old AC30 from a guy back in the seventies; for about £60 if I remember the figure correctly. This was at a time when Vox amps werenít sort after. Tim further explained that this same guy had re-covered the amp too! Now, I would use the term "re-covered" very loosely! I think this is the worst attempt of re-covering that I have ever seen!

But.......things got even worse from here. A lot of the circuitry had been butchered and cannibalised too. There was an aluminium heat-sink screwed to one of the sides, along with a ribbon cable connected to the "vib-trem" switch which, under normal conditions would be only a two position switch. This was now a twelve position switch! The heat-sink had a few wire-wound resistors on it and turned out to be a crude rendering of a switchable "power-break". There was also a two position toggle switch fitted in place of one of the tremolo channel input sockets! This also had something to do with the "power-brake".

In addition to the above, a lot of the tremolo circuitry had been ripped-out to accommodate the power-break modifications, along with a few other circuit modifications too. This being the case, the tremolo was of course "non-existent".

So, Tim was asking.... "Could this all be put back to rights?" He didnít mind about the cosmetics side of things as, like the Impact head, he fully intends to restore the appearance of the amp himself. I have since given Tim all the contact details of people who I know will be to supply him with all the necessary vinyl, tubing, handles etc to get this amp put back to rights from a physical point of view. He just wanted me to do the electronics side of things as, although I am able to do the aesthetics, I prefer it that way.

Firstly I ripped out all the junk, and then painstakingly spent time on slowly bringing everything back to rights. This took a fair amount of time, but I always do things right and "stick at a job" until this is achieved.

I get a lot of e-mail saying how interesting it is to see the "jobs-done" lists, so here yet again is a list of all that had to be done:-

 

1. Fitted new 3 & Ĺ mtr power cable, refitted power plug, both fuses in plug and amp checked, OK.

2.  Ripped out all modifications as requested.

3. Changed one EL84 base (wrong type).

4. Supplied and fitted 4 modern valve retaining clips.

5. Replaced blown pilot "on lamp" bulb.

6. Rewired complete output stage on all four EL84ís including screens and grid one resistors, also rewired heater chain (wires had gone brittle!!). Replaced main cathode resistor with correct value!! (Had been changed for wrong one!?)

7. Replaced worn out/tired main smoothing capacitor.

8. After all modification removals only brilliant channel working, sourced modified wiring and put back to original with necessary components too. Both normal and brilliant channels working now at this point but, hum on normal channel!?

9. Sourced cause of hum, found all five input jacksí switches not working (one had been replaced with a toggle switch anyway as part of the modifications). Replaced with six new input jack sockets and associated components (this included one white one as-is used on the tremolo channel and was the missing one anyway).

10. Sourced dreadful modifications to the tremolo channel, found problems and all put back to rights now, including associated components and rotary switches.

11. Cleaned top panel as best as possible and repositioned all chicken head knobs correctly. Replaced one broken grub screw in one knob.

12. Repositioned power "on-off" switch correctly with missing "under-nut".

13. Replaced a few components on main tag boards, mainly capacitors, leaving all original components wherever possible, working and still within tolerance.

14. Supplied all five missing pre-amp tubesí screening cans.

15. Two of the ECC83ís were faulty, however one of these was wrong anyway, have replaced the faulty one and changed the other for an ECC82 which it should have been!

16. Replaced "worn-out" grub screws in speaker connecting block!

17. Replaced all hardware in the form of cage nuts, M5 screws, penny washers etc (many were missing) also all other hardware checked for tightness including handles, castors, speakers and baffle screws.

18. Full rewire of the speakers.

19. Fitted "floating" jack socket for tremolo foot-switch.

20. Supplied heavyĖduty foot switch as requested.

21. Supplied premium quad set of JJ EL84ís (these are good! The Mullard GZ34 rectifier is still fine and has been retained).

 

 

So everybody, there you have it once again. Iíll let Timís e-mails tell you the rest of the "yet again happy ending story":-

Mail received a day or so after picking up the amp:

"Hi John,

 Ethan and I didnít get much time to try the amps out last night but the initial impressions are:

1). The Vox is brilliant - I've just got to re-learn how to get the best possibilities out of it but first impressions are it still has the one good sound I used to get out of it and it now has a whole bunch of other possibilities!!

2). The Impact is a revelation. The bass channel is great but, it makes the Celestion Greenback speakers flap a bit at 60%. The Treble channel is a fantastic 70's style distortion at 50% and this is before I've had time to put the JJ EL34s in.

I look forward to a more detailed try out at the weekend.

Thanks very much, from two satisfied customerís, I'll be in touch soon with the additional pictures and comments later.

Many thanks for your hard work, time and effort, Tim."

Testimonial email received a couple of months after the amp was repaired: 

John has got my old 1962 VOX AC30 working better than it ever has in all the 29 years I've owned it. It may still look ugly but it sounds beautiful!

I bought my very battered Vox AC30 in 1977 from a second hand shop in Newcastle. It was a time when Vox's were out of fashion, so between me and the rest of our poverty stricken student band we bought 3, very cheaply and I got the cheapest and most battered but it still sounded wonderful. Unfortunately some deranged incompetent had stripped the original covering and modded it. But at least one of the channels worked like they should and it had the Alnico Vox speakers.

I used it on and off with minimal maintenance until it died around 2003 and then I had a bit of a dilemma. If I took it to a repairer they might fix it but really I wanted to restore it to the original circuits and maybe even get the Vibrato/Trem working! I decided to try to find an engineer who was competent enough to restore the wiring and get it working like it should but wouldn't cost the earth. I talked to several but some did not inspire confidence at all, some couldn't be bothered, some wanted a big fat blank cheque and some were willing to have a go but had no experience of restoration. I found John's website and quizzed him about the job and looked at the work he had already done on other peoples AC30's and I finally had the confidence to put my favourite amp under the surgeon's knife (or should that be soldering iron?).

3 weeks later I collected what is still the ugliest VOX on the planet but it now sounded like it should - and some!. The Vib/Trem was a revelation and all 3 channels sang sweetly. It still hums just a little but who wouldn't after 44 years? John uses quality parts and lots of skill, attention to detail and TLC and he doesn't charge boutique prices. He also fixed my son's Impact 60 head and that too is brilliant. I can unreservedly recommend anyone to get their valve amps fixed by John and I will happily ask him to service and repair 3 other amps I have that need some TLC.

Now all I need is to complete the cosmetic refurb on my VOX

Tim.

 

Thank you so much for looking, cheers, John.

 

PHOTOS TAKEN BEFORE WORK COMMENCED:

 

Before the back panel came off.

 

........and after removal of the back panel!

 

The "power-break"!!!

 

Ribbon cabling to the "power-break".

 

 

"Sloppy" wiring to the speakers!

 

The chassis as first removed.

 

WORK UNDERWAY:

 

 

 

New input jack-sockets.

 

New Mains smoothing cap and modern valve clips fitted.

 

The output stage fully re-wired, including all new components and heater wiring.

 

Channel wiring corrected after modifications.

 

INTERNAL RESTORATION COMPLETE:

 

 

 

 


 

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