Valve Amplifier Servicing, Repairs and Modifications
Keep your valve amplifier performing at its best. From routine servicing and fault-finding to modifications, our experienced technicians have over 25 years of experience repairing and building valve amplifiers from our dedicated workshop just south of Bristol.
Servicing and Repairs
Fault Diagnosis
Our experienced amp technicians undertake all servicing and repairs for valve amplifiers. We charge £45 for an initial inspection to diagnose any issues. This service includes:
Testing all your valves
Cleaning all the pots
Cleaning all your jacks
Cleaning all the valve bases
Checking the bias of the output valves (if possible)
Once we’ve had a look at your amp, we’ll let you know what we recommend and, if it needs repairing, give you an idea of the cost before we get started. Any parts or materials needed will be charged separately.
Give us a call and we can discuss your requirements.
Our Repairs Workshop
Our purpose-built workshop just south of Bristol means that we can offer valve amplifier repairs to the West Country.
Rebuilds
Sometimes we cannot mend your valve amp (or it’s not financially viable). In that scenario, we always offer the option of rebuilding your amp using point-to-point hardwired techniques. We reuse as many of the original parts as possible, keeping the costs to a minimum.
Please be aware that the amount of work that can be carried out on some PCB circuits can be limited due to original construction techniques and design.
Top Tip
Before you take your valve to any tech to have a look because it’s not working, make sure you:
Have all leads connected properly (including speaker cable).
Ensure all those leads work.
Plug your guitar straight into the amp, bypassing all pedals and effects.
Ensure all volumes, including your guitar, are turned up.
It may sound obvious, but it eliminates all other possibilities before you start spending money.
Modifications to Your Amplifier
Looking to get more from your amplifier? We have years of experience upgrading and modifying top-end valve amps, including Fender valve amps and Marshall valve amps. Please contact us to discuss modifications or improvements.
Common Valve Amplifier Issues & Repairs
Over 25 years of working on valve amplifiers means we’ve seen a lot of faults. Here are some of the issues we regularly help musicians with.
Issue: No power, no lights, No sound…..nothing.
Common cause: Mains fuse blown.
How to fix it: Replace fuse with manufacturer’s recommended rating eg T2A 250v. Do not use a higher rated fuse as you may cause damage to your amp. If the fuse blows immediately, take your amp to a tech as this would indicate a problem within the amp.
Issue: No sound, heaters on valves light up and indicator light comes on.
Common cause: HT fuse blown.
How to fix it: Replace fuse with manufacturer’s recommended rating eg T500mA 250v. Do not use a higher rated fuse as you may cause damage to your amp. If the fuse blows immediately, take it to a tech as this would indicate a problem within the amp.
Issue: Low power, excessive background noise.
Common cause: Valve issue (pre-amp or output)
How to fix it: It is good practice to have a spare couple of ‘good’ valves hanging round. Use your spare to swap in and out of different locations to see if it makes any difference. Only put in like for like – ie only replace a 12AX7 with a 12AX7 etc etc. Please remember that valves will only go in one way, so make sure you know what that is. Output valves and Rectifier valves have a central locating spigot which will only go in one way and they are easy to break off – be careful!
Issue: Volume jumping up and down.
Common cause: Volume control dirty, or possible dry solder joint.
How to fix it: Clean pots with a non-lubricating solvent-based contact cleaner.
Issue: Crackling and popping.
Common cause: Filter caps are leaking and too old.
How to fix it: Filter caps would need replacing. This would need to be carried out by any good tech using good replacement capacitors.
Issue: High background noise.
Common cause: Coupling capacitors are leaking.
How to fix it: The coupling caps could be letting through some DC voltage and would need replacing. An experienced tech would be required to do this.
Issue: High background noise.
Common cause: Bad earthing connection.
How to fix it: Some amps have bad earthing schemes and over time can deteriorate. Your amp can develop an annoying hiss. Good tech required to fix this issue.
Issue: High background noise.
Common cause: Dirty pots and controls.
How to fix it: Clean pots with a non-lubricating solvent-based contact cleaner.
Issue: Low output, amp not sounding as it should.
Common cause: Output bias set incorrectly
How to fix it: Lots on the internet about this. There are negative voltages that the valve manufacturers recommend that your valves should operate at. Your amp is designed around that and so it should be set up for that. However, as an end user, you may want it set slightly differently to suit your tone and gain preference. BUT, always remember: ‘If you don’t know what you are doing, don’t touch the bias’.