BanditSid

Paul, I have a schematic/service manual for the Midiverb 3, PM me your email address and I'll send it to you.

You could always try this :- [url="http://www.ebay.co.uk/itm/ACOUSTIC-FOAM-SHEETS-/150631733423?pt=UK_MusicalInstr_Access_RL&hash=item231259d8af"]http://www.ebay.co.uk/itm/ACOUSTIC-FOAM-SHEETS-/150631733423?pt=UK_MusicalInstr_Access_RL&hash=item231259d8af[/url]

I had a similar problem on my 300w 1215 combo and replaced all the capacitors on the power amp board, the amp is around 10 years old so it made sense to change them all anyway. Depending on the version of power amp you have you may need to adjust a couple of things after changing capacitors, so it would be best to pass it on to a tech if you aren't happy to do it - they should replace all the caps on a typical PA board in a couple of hours and the parts aren't that expensive, just a few quid.

The voltage regulator, IC2, may have failed - but usually they fail open and give no output at all. The most common failure on a power supply board is a dry joint, caused by components that get hot expanding and contracting with use and eventually "tearing" the solder joint apart. If you can get access to a soldering iron, or someone who can solder for you, check all the joints around the regulator and any other components that may be attached to heatsinks. There is also a possibility that the rocking back and forth you mentioned is caused by the copper tracks lifting from the PCB, in that case you need to repair them with tinned copper wire or plain insulated wire connected to either side of the faulty track.

Ed, If the wiring has been "got at" it's possibly because the jack socket has been replaced but wired up wrongly. The black (ground wire) from the batteries goes to the inner ring of the stereo socket and is shorted to the socket ground by inserting a mono plug, as used on guitar leads, which then applies power to the pre-amp circuit. This allows the batteries to be disconnected automatically when the lead is removed, but won't work if a previous repair has joined all the "black" wires together,as the power will be connected permanently.

Welcome John, great collection of kit you've had. I'd love the 67 jazz as well.........another for the "why did I let it go" list.

Does your amp have active and passive inputs ? If so,which do you use ? The passive input tends to be very high impedance, which then makes the guitar more susceptible to interference pickup. Try the active input which is usually around 10k, the gain may be slightly lower but it might help with interference pickup.

[quote name='thinman' post='1046799' date='Dec 3 2010, 08:47 PM']Does anyone have any experience of these cheap USB oscilloscopes? Are they OK for basic audio frequency diagnosis? [url="http://www.virtualvillage.co.uk/2-channel-5v-pc-usb-digital-storage-oscilloscope-new-001482-009.html"]Example item[/url][/quote] I've never used one, but it claims a bandwidth up to 3kHz, which is ok for bass but a bit too low for guitar use. The sampling rate is quoted as 4kHz, which means the highest frequency it can display accurately is 2kHz, even more limited. Once you've bought it you would need some kind of probe, proper ones cost more than the device does, so that puts the cost up again I use a Hitachi 100MHz scope, so I'm spoilt a bit, but I'm not sure it is as big a bargain as it seems.

I would check inside to be sure, I bought a 1215 and the front panel wasn't lit, but I found that the cable to connect the front panel to the EL driver board was missing, I put in a bit of screened cable and hey presto it's all back lit now.

Ceramic capacitors are designed to be used for supply decoupling, where you want to remove any high frequency noise on a supply line, they were never designed to pass quality audio. The best choice for audio is polypropylene, you will get most values you need for guitar use in a polyprop capacitor.

[quote name='witterth' post='866606' date='Jun 13 2010, 11:23 PM']Id say most certainly a valve issue,and they can cause all sorts of mayhem if you get a "bad" one. there is a thing about valves thats like light bulbs (IMO) some run,and run,and run forever some just.. go... and thats it. because they are like big power storage things and are effectivley quite an old technology they do just "messup" once in a while. its cos they make Bass amps sound SO GOOD that manufacturers still use them. If you want to replace one yourself btw, treat a valve like a halogeon bulb for your car IE no touchy touchy with bare hands no expert but it is informed waffle!! W[/quote] The valve stage is there as an effect on these amps, so it will have no effect on the amp if switched out. It's possible that the cables that connect the PCB.s together are the problem, the plugs can give problems when they age. Removing the plugs and soldering the leads directly to the PCB's is the best solution.

I have three NOS Mullard EL34's for sale if they're any good to you - the date code etched in puts them as 1973 to 75 manufacture - all unused, in boxes and pe4rfect condition.

[quote name='The Marlin' post='682626' date='Dec 12 2009, 11:03 PM']Hmmmm...... I thought it was passive to active, but picked up mine used, and no info was provided on bass features. So, was most likely an assumption. Regardless, the mod fixes the isses and makes a heck of a difference. Cheers Marlin[/quote] What was the mod he did?