Watkins Dominator - UK Vintage Radio Repair and Restoration Discussion Forum

Danday56 · 20th Apr 2021, 4:53 pm

Hi All
I am attempting to repair a 1960's Watkins Guitar amp, for a friend, simple 6 valve design.
it has a normal amp input which is working, it also has a tremolo input which runs through valve no 2, this is not working. Available circuit diagram is not particularly good. I've got a bit lost, anybody in the Essex area able to give me a hand please. Many Thanks.

Kyri · 20th Apr 2021, 5:59 pm

Hi, this might be of some help, maybe?

https://www.youtube.com/watch?v=TA1U5RwGxEM

Alistair D · 20th Apr 2021, 6:27 pm

You may be able to find a better schematic here

http://wem-owners.com/schematics/dominators/

Al

Techman · 20th Apr 2021, 6:37 pm

Just to note on that video that he first calls the main smoothing capacitor a rectifier, or rectifier capacitor and then later on he gets confused again and points to the black earth wire going to the capacitor which he then refers to as a valve. I think he's just confused and probably does know what the parts are - hopefully!

This reminds me of another video I happened to see recently where some American guy was repairing a spring line reverb amp for someone who had supplied a supposedly good, but second hand spring line (or 'tank', as they like to call them) for the guy to fit. So he put his meter on the low ohms range and proceeded to measure the input transducer, he then went to the output transducer with the meter set on the same range and pronounced it dead! So at great expense (to the customer) he bought a brand new spring line unit, but just too demonstrate for the video he proceeded to measure both the input and output coils of the new unit to show the difference. I was waiting with bated breath for him to find the exact same open circuit output coil as the two old ones, but he went and used a different meter, some autoranging thing, I think...I could see the meter he used originally still on the bench and still set to the same low ohms range. I honestly don't know whether the guy was being deliberately devious or whether he simply didn't know what he was doing, so you have to be wary of some of these YouTube 'experts', although many of them are very good.

As for the OPs fault, as always, download the appropriate valve data and measure valve voltages around that particular valve, ie, DC voltages, not the AC heater voltage, and then go from there.

Diabolical Artificer · 21st Apr 2021, 6:23 am

The tremelo is activated by a foot switch which you have to plug in for it to work. I fitted a switch on the back of mine, all it does is ground the oscillator valve.

Another mod is to fit a seperate on/off SW as these amps suffer from hum.

Andy.

Craig Sawyers · 21st Apr 2021, 7:34 am

Although Charlie Watkins has been dead for 7 years, his potted history site is still up and running http://www.wemwatkins.co.uk/history.htm .

Although he didn't mention it, the iconic Pink Floyd at Pompeii video shows their row of WEM speakers behind.

When I was fixing a Dominator Bass for my son, Watkins was still alive and answered the phone when I called. Amazingly helpful guy. Now giving the choirs eternal a dose of hearing damage.

Craig

Danday56 · 8th Jun 2021, 7:11 pm

Hi

Thanks for the advice, got it all working now, but, if i plug a guitar in the tremelo side and the plug into the microphone side it is quite a bit louder. looking at the cct the input to the tremelo has resistors in cct, so i assume this difference is correct.

8th Jun 2021, 9:21 pm

I went to Chertsey Museum a couple of weeks ago, their special exhibition room had lots of WEM stuff in there. A small museum, worth a 20 mile trip in my opinion just to see that. Check first, they do change frequently.

Diabolical Artificer · 9th Jun 2021, 6:25 am

Quote:

Originally Posted by Danday56

so I assume this difference is correct.

Yes.

20th Apr 2021, 4:53 pm	#1
Danday56 Triode Join Date: Oct 2017 Location: Southend-on-Sea, Essex, UK. Posts: 12	Watkins Dominator Hi All I am attempting to repair a 1960's Watkins Guitar amp, for a friend, simple 6 valve design. it has a normal amp input which is working, it also has a tremolo input which runs through valve no 2, this is not working. Available circuit diagram is not particularly good. I've got a bit lost, anybody in the Essex area able to give me a hand please. Many Thanks.

20th Apr 2021, 5:59 pm	#2
Kyri Tetrode Join Date: Mar 2021 Location: Lancashire, UK. Posts: 57	Re: Watkins Dominator Hi, this might be of some help, maybe? https://www.youtube.com/watch?v=TA1U5RwGxEM

20th Apr 2021, 6:27 pm	#3
Alistair D Nonode Join Date: Jan 2010 Location: Edinburgh, UK. Posts: 2,008	Re: Watkins Dominator You may be able to find a better schematic here http://wem-owners.com/schematics/dominators/ Al __________________ I won't tell you how I discovered that.

20th Apr 2021, 6:37 pm	#4
Techman Dekatron Join Date: Nov 2009 Location: Lincolnshire, UK. Posts: 5,000	Re: Watkins Dominator Just to note on that video that he first calls the main smoothing capacitor a rectifier, or rectifier capacitor and then later on he gets confused again and points to the black earth wire going to the capacitor which he then refers to as a valve. I think he's just confused and probably does know what the parts are - hopefully! This reminds me of another video I happened to see recently where some American guy was repairing a spring line reverb amp for someone who had supplied a supposedly good, but second hand spring line (or 'tank', as they like to call them) for the guy to fit. So he put his meter on the low ohms range and proceeded to measure the input transducer, he then went to the output transducer with the meter set on the same range and pronounced it dead! So at great expense (to the customer) he bought a brand new spring line unit, but just too demonstrate for the video he proceeded to measure both the input and output coils of the new unit to show the difference. I was waiting with bated breath for him to find the exact same open circuit output coil as the two old ones, but he went and used a different meter, some autoranging thing, I think...I could see the meter he used originally still on the bench and still set to the same low ohms range. I honestly don't know whether the guy was being deliberately devious or whether he simply didn't know what he was doing, so you have to be wary of some of these YouTube 'experts', although many of them are very good. As for the OPs fault, as always, download the appropriate valve data and measure valve voltages around that particular valve, ie, DC voltages, not the AC heater voltage, and then go from there.

21st Apr 2021, 6:23 am	#5
Diabolical Artificer Dekatron Join Date: Jul 2009 Location: Sleaford, Lincs. UK. Posts: 7,662	Re: Watkins Dominator The tremelo is activated by a foot switch which you have to plug in for it to work. I fitted a switch on the back of mine, all it does is ground the oscillator valve. Another mod is to fit a seperate on/off SW as these amps suffer from hum. Andy. __________________ Curiosity hasn't killed this cat...so far.

21st Apr 2021, 7:34 am	#6
Craig Sawyers Dekatron Join Date: Nov 2010 Location: Oxford, UK. Posts: 4,983	Re: Watkins Dominator Although Charlie Watkins has been dead for 7 years, his potted history site is still up and running http://www.wemwatkins.co.uk/history.htm . Although he didn't mention it, the iconic Pink Floyd at Pompeii video shows their row of WEM speakers behind. When I was fixing a Dominator Bass for my son, Watkins was still alive and answered the phone when I called. Amazingly helpful guy. Now giving the choirs eternal a dose of hearing damage. Craig

8th Jun 2021, 7:11 pm	#7
Danday56 Triode Join Date: Oct 2017 Location: Southend-on-Sea, Essex, UK. Posts: 12	Re: Watkins Dominator Hi Thanks for the advice, got it all working now, but, if i plug a guitar in the tremelo side and the plug into the microphone side it is quite a bit louder. looking at the cct the input to the tremelo has resistors in cct, so i assume this difference is correct.

8th Jun 2021, 9:21 pm	#8
Guest Guest Posts: n/a	Re: Watkins Dominator I went to Chertsey Museum a couple of weeks ago, their special exhibition room had lots of WEM stuff in there. A small museum, worth a 20 mile trip in my opinion just to see that. Check first, they do change frequently.