Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Default Watkins Westminster combo from 1964

As this one
http://www.ampaholics.co.uk/watwest%20frnt.jpg
one of the rare 2x10 inch speaker ones.
4 plus 2 valves does not agree with the schematics I've found so far out
there, any pointers?
Not safely in a position to remove the valves yet but only a military CV
number seen so far on one of them, and I suspect most faded to nothing .
If no schematic found will have to try and find the little etched numbers as
no valve chart inside the cab
The owner wants to go out using this again , he bought new in the 60s, 2
repairs in the 70s but I cannot see the cones lasting out, they feel like
tissue paper, despite kept indoors of a house for decades .
Mains cable needs replacing , as does the corroded small electros, I assume
the big one with the (6?)426 datecode will need restuffing/replacing. Ser
no. in the 400s . All the carbon resistors are readable and othewise for its
age looks healthy, even the strange cab screwcaps are present.


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Default Watkins Westminster combo from 1964

All the steelwork is corroded a bright sulphur-coloured lemon-yellow. I
don't remember seeing that before, actual sulphur? I'll try scraping off and
burning some
I've recorded all the R values sequenced through the amp
A previous repairer had marked V1? and V2 ? positions as ECC83, the op
bottles are CV2975 so EL84, RR is marked EZ80 leaving just the valve
posistioned as ,and wired cusory-looking as , a splitter driver V3? it looks
like a double triode and I will test as ECC82, has 4OD etched on the
envelope , when I dig out those crib sheets for that.


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Default Watkins Westminster combo from 1964

With a bit of fossiking about , looks as though this is a close enough
schematic
http://web.archive.org/web/200606271...ronics.com/The
_Archives/Watkins_Dominator_15.jpg



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Default Watkins Westminster combo from 1964

On Apr 12, 8:20*am, "N_Cook" wrote:
All the steelwork is corroded a bright sulphur-coloured lemon-yellow. I
don't remember seeing that before, actual sulphur?


Not a zinc dichromate or cadmium plating?

I'll try scraping off and
burning some
I've recorded all the R values sequenced through the amp
A previous repairer had marked V1? and V2 ? positions as ECC83, the op
bottles are CV2975 so EL84, RR is marked EZ80 leaving just the valve
posistioned as ,and wired cusory-looking as , a splitter driver V3? it looks
like a double triode and I will test as ECC82, has 4OD etched on the
envelope , when I dig out those crib sheets for that.


Looks like guitar amp repair keeps you folks in business. Do you do
your own reconing, or do you have favorite people to do that? Can they
match the cone and fundamental resonance fairly close, or does
reconing inevitably change the sound?
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Default Watkins Westminster combo from 1964

spamtrap1888 wrote in message
...
On Apr 12, 8:20 am, "N_Cook" wrote:
All the steelwork is corroded a bright sulphur-coloured lemon-yellow. I
don't remember seeing that before, actual sulphur?


Not a zinc dichromate or cadmium plating?

I'll try scraping off and
burning some
I've recorded all the R values sequenced through the amp
A previous repairer had marked V1? and V2 ? positions as ECC83, the op
bottles are CV2975 so EL84, RR is marked EZ80 leaving just the valve
posistioned as ,and wired cusory-looking as , a splitter driver V3? it

looks
like a double triode and I will test as ECC82, has 4OD etched on the
envelope , when I dig out those crib sheets for that.


Looks like guitar amp repair keeps you folks in business. Do you do
your own reconing, or do you have favorite people to do that? Can they
match the cone and fundamental resonance fairly close, or does
reconing inevitably change the sound?

+++

Unlikely a plating as all different makers/sources of steel, valve base
skirts,
retainer springs, pot casings and large capacitor clip all bright powdery
yerllow. Against that - the mains Tx someone has replaced and the steel
frame of that is normal colour , so perhaps some tropicalizing or spraying
by
the maker that has deteriorated . The op Tx is stove-enamelled so grey
colour.
Another thought , as stored under the stairs, if the household gas
supply/meter is there and whether long-term so undetectable by human nose,
North Sea gas leakage, gives off sulphur component that reacts with steel ?


The only reconing I've done is where I can remove a couple of turns of VC or
a repairable braeak at a bend of the VC tails , but I do have an 18 inch
speaker and cone that I will sometime? try rewinding the broken VC as the
former is not burnt beyond a 2mm x 1mm spot

The prices of new cones I've seen means the usaul response "well I may as
well buy a complete new speaker for that cost"




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Default Watkins Westminster combo from 1964

I scraped off some of the yerllow and it did not go orange then red then
Hadean smell on heating so perhaps some sort of steel passivation or
tropicalizing treatment


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Default Watkins Westminster combo from 1964

Just wasted an hour testing the double rectifier.
No response on "goodness" test for either rectifier.
Had an untested EZ81 knocking around and no reading on that either , semed
unlikely . The owner tried out this amp and some amplification, but
unuseable, for other noises and soon switched off.
As EZ80 / 81 uses the same socket as ECC81/82 unlikely a wiring problem
there and expected to have to dive into the big bakelite multiway thumbwheel
switch bank.
Just about to try 2x 1N4007 in the socket and thought I'd check the Avo, 9
digit code from first principles. My 1968 Avo valve data book for EZ80 and
81 has setting code
7*1 23* 6**
(for amplifier anodes , not diode anodes) but it should be
8*1 23* 9**
in this particular case
801 230 900


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Default Watkins Westminster combo from 1964

so googling around that came to
http://www.vintage-radio.net/forum/a...chmentid=37962
and have left a note to myself, the next time I'm inside this Avo valve
tester, to modify the meter protection


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