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Hi all, new here but it seems to be a great, knowledgeable place for the old Vox amps. I just picked up a Vox Buckingham. I've had a Sovereign cabinet forever just sitting around and this came up on my local craigslist for a pretty good price so I couldn't pass on it. The amp itself works "mostly" fine. The normal channel is good, both inputs. Eq works as it should. Tremolo across all channels is good. Bass channel is good. Only issue is the brilliant channel is very low volume and sounds a bit distorted. It also doesn't work with the reverb switched to off or Normal. Only with the reverb selector set to brilliant so I'm not sure at this point what that indicates. I have the schematic I downloaded after reading this post: https://music-electronics-forum.com/...ad.php?t=41151 and I'm very experienced at electronics and am a professional electrician and technologist so can find my way around a circuit board. At some point I'll replace all the caps but would like a couple of hints at a starting point if anyone has seen this before in these things. I'll post some pics in a while. Also the reverb itself sounds very drippy, almost like a fast tremolo so I'm not sure if that's good or not. Doesn't sound at all like my AC15 reverb, anyways. Anyways, aside from missing a couple of knobs and looking used, it's a great looking setup now. The tremolo is really cool sounding...
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Lucky you!
Anyway, I've worked on many of these and one of the members has detailed information on a site for repairing and restoring these amps.
This info has served me well over the years so go to geofex.com and there's a whole section describing everything you'll need to know. -
Thank you!Comment
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Lots of reading there, haven’t found my exact issue but tons of good info. I’ll get some pics up tonight or tomorrow, looks like I have to have them hosted on a URL for this board?Originally posted by drewl View PostComment
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Welcome to the place.
If the brilliant channel only works when the reverb is switched to brilliant, then the first thing I would check is the shielded cables that connect to the reverb switch. You should also test the switch itself.
What does NAD stand for?
The trem should only work on the normal channel. If you are talking about a tube AC-15, then the reverb will sound completely different.Comment
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NAD - New Amp Day
or new to me, anyways. I’ll test the switch and cables in the next day or so-I haven’t popped it apart yet. The switch is suspect for sure-previous owner noted that it needed to be in just the right spot to work but I haven’t got it there and it’s quite scratchy and poppy right on that contact. Fine on off or normal channel. I’ll take some contact cleaner to it as well.
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Small update, yes the trem only works on he normal channel. The cable to the switch is original and the shield, while attached, looks corroded. I can get the brilliant channel fully working if I get the reverb switch to sit “just so”, very small working contact point. Also if I set the reverb switch to off or normal the brilliant channel passes no sound but if I set it to off or brilliant the normal channel works fine, just no reverb, as you’d expect. So I’m not sure I want to start throwing in parts I don’t need to just yet, I’ll try to clean the switch with deox-it or something. Also, how exactly do you get this thing apart? It looks like tiny hex screws screwed up into the top of the head from the inside. I’d like to disturb as little as possible.Originally posted by 52 Bill View PostComment
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Small update 2, it's definitely looking like the reverb switch. The brilliant channel DOES work, again have to fiddle with the knob in all positions. So if a shot of Deoxit doesn't do it, is it possible to find replacement switches or equivalent parts for that reverb switch?Comment
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Ok, back with some pics. I got the chassis out and gently lifted the circuit board and sprayed Deoxit on the reverb switch. Did help a small amount in the sense that it's easier to find a connection when on the brilliant channel but now after playing a while on it the sound distorts if I hit a loud or busy chord. The normal channel has noticeably less volume than the brilliant or bass channel as well now. Bass channel is still fine, no issues. I can also hear a pulsing background hiss that is obviously through the tremolo somehow as I can change the rate and amount by turning the tremolo controls. This is heard over all channels. I'm sure I did something when I took the chassis out even though I was as careful as I could be.
Also, for some reason the reverb pan only has one spring in it. I was hoping to avoid getting into a wholesale cap/parts change-out but is that what it seems like now? I'm trying to read as many forum posts on these things as I can find...
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You have a Buckingham head with a different cabinet. One thing to check is what the speaker cab impedance is. I think that that version of the Buckingham is looking for an 8 ohm load.
The reverb tank is missing one of its' springs. Are the hooks that hold the missing spring still there or have they been broken off? If the hooks are still there, the spring can be replaced with one from a dead tank.
Try cleaning the reverb switch and slowly rotating it through the three positions. It may take a few times to get it clean enough not to mess with the signals. The switch can be replaced, but unless it is physically broken, there usually is no need to replace it.
There are many things that can cause the distortion or loss of signal, but the usual suspects are the electrolytic signal caps in the preamps. Weak or leaky transistors can also be a problem. R.G. will tell you to just go ahead and change all of the electrolytics, probably not a bad idea. I can usually recap an entire preamp in about an hour, but you have to be organized and have all of the parts handy.Comment
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Here’s a source for your knobs and a description of how the controls are supposed to work:
http://www.voxshowroom.com/us/amp/buckCP.html
I would clean all of the controls and switches... well. Also you need a footswitch for some of the stuff to work like the fuzz.Comment
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Thanks for your reply, much appreciated. The Sovereign cab is 4 ohm but I’ve wired in another 4 ohms in series with the jack so the Buck is seeing 8 ohms. The reverb’s second spring hooks are gone so I’m trying to source a replacement. The closest I’ve found I think is this one: https://www.amplifiedparts.com/produ...nk-mod-4bb2a1bOriginally posted by 52 Bill View Post
I think I may have overdone it with the deoxit and some residue caused a bit of shorting because I just finished playing the last hour or so and the normal channel is back to regular volume and the brilliant channel is much more stable through the switch so hopefully the deoxit did it’s job.
Re-capping is definitely the medium term goal, I’ll just have to get a parts list together to get all the right pieces, i’d like to have this apart as little as possible.Comment
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Thanks, I’ve been looking at that site a lot! I have some replacement corners and knobs from eBay on the way so I’ll have it tidied up cosmeticallyOriginally posted by olddawg View Post There’s a guy on eBay who makes circuit accurate replacement foot switches as well. They’re not in original enclosures but they work so I’ll probably pull for one of those if I can’t source an original. I want to get it functioning solid first.
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Are you sure about that. Your spkr cab pic above shows 4 speakers wired in series/parallel. If they are 8R individual speakers then your cab would be 8R. It would take 4R speakers to make a 4R cab and I think thomas vox used 8R spkrs.Originally posted by Mamm7215 View PostKeep learning. Never give up.Comment
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Fairly sure, the label on the back says 4 ohms and when I meter out the jack I get 8.2 ohms...Originally posted by Reader View PostComment
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