CHAMP ELECTRONICS -" THE VALVE AMP HOSPITAL"

NOTTINGHAM, ENGLAND

 

REPAIR OF THREE VOX AC30 COMBO AMPLIFIERS

 

"Hello all. About four years or so ago (as at 2006) I did some recording in a local studio, near to my hometown of Nottingham, UK. This recording required me to play the bass lines on a new album by a tribute band to the late, great, Billy Fury who was Britain’s answers to Elvis Presley and of immensely tremendous success during the early 1960s, although mainly in the UK. I also did a lot of backing vocals and various percussion work on the session too. At the time of doing this work I became quite friendly with the owner of the studio, who is called Ian. He also plays bass guitar in a band called “The Silver Beatles”. They mainly work abroad, in Germany. (Web-site: http://www.silverbeatles.de ) I actually stand in awe of Ian as, although he was able to play bass anyway, he took it upon himself to learn to play the bass “left-handed”! This was purely for cosmetic reasons as he wanted the band to be as close as possible to the original Beatles as possible. I don’t think that I could have ever made myself do this! Bravo Ian! 

Now, being a Beatles “Tribute Band”, they of course, use all Vox amps. Although not hearing from Ian during this four year period, I did in fact receive a phone call from him one day in 2006 to see if I could basically service and sort out all the Vox amps that they used on stage. together with their spare amps. Of course none of this was a problem to me, and so Ian proceeded to bring all the amps for a service/repair, one at a time. This allowed me to compare the different versions that have been produced in three different eras during the life-span of the AC30. Here are the results:-

 

1. VOX AC30 - LATE 1970s

 

 

This was the first one brought around, so it was the first one to be tackled. Out of all the Vox re-issues that there have been, this is one from the late seventies.....and what a heap of junk it is!! It’s a shame that the VOX name was ever allowed to have been put on this piece of ****. The design of it is disgusting, the flimsy printed circuit board is cheap-tack, and most of the used components are cheap-tack too. I wouldn’t give this re-issue “house room”, but it is a job and needs to be done. All the circuit boards had to be painstakingly removed before it was possible to even start work on it! 

 

 

 

 

 

 

I had to change many dead and tired components, as I’m sure you can see in the photo. Amongst all the listed faults were: poor sound, very noisy, no tone, vibrato not working, noisy potentiometers, keeps blowing power fuses (even a 10 amp fuse! I’m not surprised as the GZ34 rectifier tube was faulty here), speakers need a rewire…..the list goes on! After all the electrical component changes, a clean and spray of all the pots, plus replacing a couple of them, a new GZ34, one ECC82, a full set of JJ EL84’s, correct 3 amp power fuse,............... In-fact, here is the original invoice list, which makes describing the work required much easier:

To Repairs/Service On Vox AC30 70’s Reissue Combo:

1. Removal of main circuit board for many component changes and servicing of most of below. 

2. Spray & clean all potentiometers (replace two) & valve bases. 

3. Supply 1 x matched quad set of premium JJ EL84 output tubes. 

4. Supply 1 x JJ GZ34 rectifier tube. This was the cause of the blowing fuses! 

5. Supply 1 x Mullard ECC82 tube (on tremolo circuit). 

6. Replace many components in the form of resistors/capacitors (please see returns bag). 

7. All nuts, bolts, screws, washers, hardware checked & replaced as need be. This includes the tightening of the handles, baffle, input sockets, power switch, all controls, corner brackets and the feet. Also replaced the two missing feet and changed the rusty screws on the remaining pair. All new backs’ screws and cup washers + correct M5 cage nuts. Correct spacer washers now on amp under main wooden board, plus correct Allen bolts/penny washers too. Many were missing! 

8. Rewired mains (power) cable and fixed proper anchorage to chassis, removed taped-up junk. 

9. Cleaned and straightened main control panel as best as possible. 

10. Hovered and cleaned inside of case. 

11. Fitted correct 3 amp power fuse. 

12. Replaced full set of “black chicken head” knobs. (many were cracked or broken). 

13. Rewired speakers with correct cable as requested. 

14. Both speakers found to be faulty, replaced both of these (supplied) also with missing plain washers. 

15. Re-soldered all four output tube bases (very dry!!). 

16. Traced and sorted “non working tremolo” One of the tremolo switches had been changed and wired incorrect!!?....the tremolo would never have worked wired in this fashion! 

17. Replaced worn out “grub screws” in speaker connecting block!!? 

18. Supplied and fitted tremolo foot switch “flying lead” in-line jack socket. 

19. Supplied missing tremolo foot switch. 

20. Approximately one and a half full days work, including collection/pick-up (fuel) of knobs and power-tubes from Snenton, Nottingham.

 

 

Results: Good, clean, perfect 34.28 watts RMS @ 16 ohms. All back to rights, should “kick-ass now” and it sounds pretty good! Though not one of my favourite Vox re-issues, at least it’s all working again now………..Phew!

 


 

2. VOX AC30 30th ANNIVERSARY LIMITED EDITION - 1990

 

 

Now we’re looking at 1990 30th Anniversary Limited Edition beige model. OK, still on a printed circuit board but what an improvement! This is a much more solid, with a fairly well designed circuit board and a layout that is much more “service engineer friendly”. The instructions/faults supplied with this one were as follows:- "Crackles and pops when switched on, volumes crackle badly, dry joint or loose valve base? some distortion after long use." All the control problems were soon sorted with an electronic engineer's “best friend” switch cleaner! 

 

 

 

 

 

 

 

 

 

Once again, the original invoice is a better, more thorough explanation of the actual work required:-

To Repairs/Service On Vox AC30 90’s Limited Edition Reissue Combo

1. Removal of output tubes’ circuit board for access to faulty tube base(s) *This was the cause of the crackle!* 

2. Spray & clean all potentiometers & valve bases. 

3. Supply 1 x matched quad set of premium JJ EL84 output tubes. The quad of Sovtek’s were well down and crap anyway! 

4. Supply 1 x Tungsram ECC83 tube (the Sovtek in here was crap on high frequencies!). 

5. Supply 1 x Tungsram ECC82 tube (on tremolo circuit again, also had the wrong tube in here, ECC83?). 

6. All nuts, bolts, screws, washers, hardware checked & replaced as need be. This includes the checking and tightening of the handles, baffle, speakers, input sockets, power switch, all controls and corner brackets. Replaced missing screw on tubes cover and fibre washers on power tubes board. (left off by a previous engineer?). 

7. Fitted four new feet and screws as requested. 

8. Checked for correct 3 amp power fuse, ok. 

9. Re-soldered all four output tube bases (very dry and one loose in the print!!). 

10. Approximately a full days work. More than I bargained for but she is at least done correctly now!!

 

Results: Good clean perfect 32.57!! watts RMS @ 16 ohms. Another phew! 

 

 

 

 

 


 

3. VOX AC30 - LATE 1980s

 

 

At last we are now talking a decent bit of kit! This late eighties reissue is lovely. If I have anything at all to complain about it is the fact that they haven’t used the GZ34, but have used silicone rectification instead, which changes the sound a little bit. What a shame! But, nevertheless with the original type tag boards and virtually identical layout, this was my favourite one. Needing much less doing than the previous two, the fault-list on this one was as follows:- "Vibrato-tremolo pot loose and not working correctly, all controls a little noisy, distortion after prolonged use, power flex a bit iffy, tone needs improving."

 Yet once again the original invoice explains all:-

To Repairs/Service on Vox AC30 80’s Reissue Combo:

1. Replace busted tremolo switch and knob too. 

2. Spay all potentiometers. 

3. Re-align all chicken head knobs. 

4. Supply and fit missing feet. 

5. Re-wired power cable and new anchorage clips too. 

6. Sorted distortion in the form of 1 x faulty ECC83 (this corrected the tone issue too. All the other tubes were fine).

 

 

 

 

 

 

Results: Good clean perfect 33.17!! watts RMS @ 16 ohms. This is a nice amp and sounding pretty good too!

 


So everybody, there you have it. Three Vox amps all in a row. All from different decades and all with different problems. But…….all done now!

Ian has since telephoned me with thanks, and also informs me that they are all “doing the biz!”

Cheers, John."

 

 


 

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