Valve Ampathon – Marshall – Sound City – Fender – Selmer

This week it seems everything that came through the doors, had a valve of some sort in it. This is not a bad thing, as we really do enjoy working on Valve units.

The first item through the doors was a Marshall JCM 2000, this amplifier was bought to us because the re-verb was not working. To fix the issue we refurbished the re-verb tank, we also carried out a max power test after re biasing the output valves.the unit is now back with the customer who is very happy with the results.

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Watkins Copicat, Vocal PA, Guitar Amplifiers. Just a few from a very busy week!

This week has been fairly busy, and we have had a couple of very interesting and unusual units, one of these being a Watkins ( Wem) Copicat. This unit is used for vocal PA applications to give echo to voice, and also used for guitar. Its basically an analogue echo effects unit from the 60’s 70’s. From the picture ( right) you can see that there are 6 heads, from left to right the first head after the roller is the record head which records the input from the mic or guitar, to the tape. The next four heads are playback heads and are used to give varying amounts of delay. The last head in the chain is the erase head which removes all data from the tape. This one has been bought into us for a full service, to ensure it stays usable and reliable.

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Pioneer CDJ-1000MK3 and Vestax DJ Mixer In For Repair

This first item we had through from our website this week was a Vestax DJ mixer, it was suffering from a bent selector switch, which was fairly straight farward to repair. It is  now repaired and will be making its way back to the customer shortly, we hope they are very pleased with it.

It was a busy week it seems for DJ equipment, as soon as the Mixer was fixed, the bell on the counter went and a gentleman with a Pioneer CDJ was waiting to be seen.

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Incorrectly Wired Plugs Could Potentially Kill! Check your Plugs!

On Monday I had a chap bring in his amplifier, he was having some trouble getting it working.

Whenever we get any items in, we ALWAYS check the plugs to make sure they are wired correctly before we start doing any other work.

We found that the plug was wired completely wrong with the neutral fitted to the earth pin!

This was not the cause of the fault on the unit, but could potentially cost someone their life!

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Speaker Specification Guide Part 3 – RMS

RMS explained

What is RMS?

RMS is an abbreviation of the term “Root Mean Square”.

When you purchase speakers they will come with a rating. Good quality speakers always come with an RMS rating, this is the the power capability of the speaker before distortion occurs. Beware of some cheaper speakers which say they are ” 1000watt” for example, this is Peak Power Output, and is basically what the speakers will cope with with distortion and is useless in most circumstances.

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Yamahaa 01X Digital Mixer & Bose Speakers repaired after having a smashing time..

This week It seems everything that comes in has been damaged through impact one way or another, the first thing to come in was a lovely Yamaha 01x digital mixer, as I’m a service centre for Yamaha I tend to get a lot of their items in.

This one was a little different though as it was not down to a fault, as much as a bit of an accident. The Input gain control channel 1 had been snapped off, along with channel 1 fader which had been bent. This had happened during a studio accident… I asked no more questions…

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Speaker Specification Guide Part 2 – The Basics

This is the first real section of our Speaker Specification Guide. Covering the main components of a speaker, and the general basics of how the speakers work.

Within this guide when we refer to speakers we are generally referring to actual speakers as opposed to a cabinet of speakers, but the principles are the same.

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Speaker Specification Guide Part 1 – Overview

Lets face it choosing the correct speakers for your set-up can be a real nightmare, there are many factors to take into consideration including Wattage and impedance.  Weather it be a small power hifi system, or a 3000watt PA system, the rules are the same. So to make this decision easier to understand there are a few very simple guidelines to follow.

This guide will cover everything from the very basics, progressing through to choosing the correct speaker for your system, and making speakers you already have work with a new amplifier.

The content will focus on the following topics, and be broken down into questions that we are frequently asked over the counter at our workshop in Worcester.

1. Speaker Specification Guide – This Page
2. Speaker Construction
3. RMS
   
4. Impedance – Not yet Published
   
5. When it all Goes wrong -Not yet published
   

Should you have any more questions once you have read through these pages, please feel free to contact us and ask, or to post on the articles themselves and ask. We will be only too happy to help!

Vox AC30 Complete Rebuild

This Amplifier was bought to me looking like something made of sections of shelf, it had no skin and looked like it had been rescued from the Titanic.

Luckily most of the electronics worked, there where a few faults here and there but nothing that could not be sorted with a bit of  investigation.

The customer who bought it to us had owned it for 15 years, and for the last 5 of those years it had sat unused and faulty, he had taken it to another “Amplifier Specialist” in the past who could not track some of the faults, and so for this reason it had been left in the state it was in when it was delivered to us for nearly 5 years!

After a bit of time this is what we returned it to:

This amplifier really was a pleasure to work on and we really cannot wait till the next one comes in!

Stage Safety

Recently we have seen a Peavey combo which had been gigged to within an inch of its life with a fault description of  ” I keep getting a shock when I touch a microphone”

First we did a safety test which it failed , this was found to be that the mains lead earth connection had been ripped out of its securing grommet & the main earth of the amp broken therefore there was “No Earth”.

The chassis was removed to reveal that the smoothing capacitors on the  power supply board were broken away from their solder joints, if  the loose end had come into contact with the metal chassis  it would make the chassis live and potentially fatal.

This is one example of dozens that we have seen over the years & from our experience we would advise anyone using mains equipment to at least have it safety tested to ensure that you dont get a shock or worse as it happens all the time!