pye mozart hfs 20

[jimangus]

hmmm, it doesn't like my esl57's, didn't last long before it threw a fit.

Any idea if it would drive them after a good service.

Also is the bridge rec suppose to be so blummin hot, ouch!!


jim

[pre65]

The amps Quad used for 57's were the Quad 11 KT66 push pull monoblocks, rated at somewhere around 15 WPC.

I doubt your Pye would manage a quarter of that.

I have heard that KEL84 will make 57's sing, so perhaps you just need more power.

[John Caswell]

Hi Jim,
Well according to my 1959 Hi Fi year book the Motzart HFS20 was rated at about 9 watts per channel so I doubt it would drive Quad ESLs very well.
I don't think it lasted in production all that long as in my next book 1970 it is missing.

John

[Richard]

Originally Posted by jimangus

Thankyou for the replies.

suprised by the lack of advice on the matter.

is this forum now defunct ?


if so where should i try to get good positive advice ?

Hi Jim,

Not sure what you were expecting, these amps are hardly common

Jonathan Hill's Audio Audio book says 9W with 200mV sensitivity so it should be good for use with a passive pot controller or active pre.

Often these old amps sound great without their preamp which have many switches and pots of uncertain condition.

It also has 4, 8, 15 ohms output adjustable so have a look and try those on the Quad 57s. Quad IIs by comparison were 12W and, with their controllers, about twice the price.

Other than that it would be nice to see the circuit but it's SE of decent output so should be quite usable

[pre65]

I would have thought 9W from a single EL34 was a bit optimistic ?

[jimangus]

Hi all,

well its thrown its fuse, after making a distubing cracking type sound. Can't see any charing but will lift the boards out later and have a look both sides.


Photo's to come as there are a couple of bits i am not sure what they are exactly !

i will also try and get the circuit diagram scanned in.


Kind regards

jim

[jimangus]

Hi all,

have dismantled one side of the amp, so that i have the other side as reference when replacing components.

A couple of pressing questions, have a capacitor either side that is strange. It has two tags on one end and one on the other. The strange thing is one of the two tags is colored red the other is not. it says the following on the cap.

Plessey
electrolytic
16-16 uf
RED OUTER
275v WKG
APR 60 (this is its date, so i wouldn't be suprised if it is knacked by now)

I am wondering if it is just a double cap with a shared neg side. if so would two separate caps with the neg joined do the trick ??

Any help would be great on this. Also 16uf is hard to get by the look of it.



secondly could any one recommend a diode type/ or a bridge rec to replace the one fitted, it operates on mains voltage by the look of it and supplies 265v. it will need to be thin as it is currently mounted behind the front plate.



kind regards

jim

[jimangus]

here is a photo of the same amp as mine, you can see the bridge rec under the front part.

http://www.vintage-hifi.2itb.com/whats_new_2.html

[Richard]

Hi Jim

Yes that's what the cap is, 2 with common negative, the Red is Reservoir and is first cap position after the bridge, the other (sometimes Yellow) is second cap after the choke or resistor. You can use 2 separate caps as you suggest, 22uF would be fine but they must be high ripple rating, miniture electros are no good and will overheat. You should be ok with something like 2 of Rifa 22uF 450V, 240mA ripple rating,
http://uk.rs-online.com/web/p/aluminium/2267283/

You can make a bridge from 4 modern diodes, schottkies, or much cheaper, using something like UF4007 1A 1000V.

It would be good to see the circ just to confirm btw.

[jimangus]

hi all circuit diagrams here.

any advice would be great. I am also having trouble sourcing 50uf caps for the pre amp and the 200uf caps in the dotted box to the right are unusual, plastic bodied electrolytic (red one end black the other) with a very low temperature of 70'C.

Also so far i have only found one bridge rec, can't see the other any where ??

Give me a bit of help as i am wondering if this is beyond me at the moment.




kind regards


jim