Quad 33 and FM3

[ppppenguin]

I have owned my 33 and FM3 from new, bought c1980. Neither has had any attention apart from the Rifa snubber which did its usual horrible trick a few years ago.

The tuner hasn't been sounding quite right recently. Perhaps a touch of distortion, perhaps a little bit of buzz. I reckon it's time for new electrolytics all round. Although CD and gram sound OK I might as well do the 33 while I've got things apart.

Although I've got the original manuals it's handy to have machine readable versions which can be found here:
http://www.vintageshifi.com/repertoire-pdf/Quad.php

My FM is the later type, s/n 31272. The 33 is also late s/n 87719.

The FM3 has several 0.68uF tantalum beads. Looking at the circuit and the MC1310 decoder data sheet I can't see any harm replcaing them with 1uF polyester in 0.2" pitch radial packages which I have in stock. Actually I have plenty of 0.68uF polyester but in rather larger axial packages which will look horrible.

Any thoughts on this?

Also anything else I should look out for?

I've looked at this: http://quadrevisionspot.blogspot.co.uk/2...notes.html and can't see any special reason to replace resistors, bulbs or transistors.

Apart from electrolytics anything to look out for on the 33? I would replace the 640uF caps in the PSU with 1000uF and if there's space the 400uF reservoir cap can be changed to 1000uF. C406 is 12uF and would be repalced with 22uF.

Does anyone know what the low power DC output on pin 4 of the 33's output socket is meant to be used for? It powers the pilot light in the 33 but that's all.

[Synchrodyne]

As far as I know, that low-power DC output was intended for the remote switching of connected power amplifiers, although I do not have a "hard" reference to back that up.  Although not used for the 303, perhaps Quad thought that with possible future and larger power amplifiers, on-board relay switching of their power inputs would be preferable to having the 33 do the switching.  But it didn't turn out that way, and the 405 followed the 303 pattern, being switched by the 33.

Cheers,

Steve   

[ppppenguin]

Steve, thanks for the explanation. Unless they are bulging I don't think I'll bother to replace the electrolytics that smooth that supply

[alanworland]

I bought my 33/303/FM3 I believe in 1970 and apart from the output electrolytics in the power amp (they leaked) is still running with all the original components!
I did know at one time what the production period was fur these units, it was much longer than most similar products. The 303's were used in the Royal Albert Hall - don't know how many.
Perhaps I also ought to consider replacing likely failures?

Alan

[ppppenguin]

I bought an early 405 along with my 33 and FM3. That's been re-capped, at the same time as I replaced a couple of blown output transistors a few years ago.

[Refugee]

Would that extra power output be for a microphone mixer?

[Synchrodyne]

The Quad 33 production run was 1967 through 1982, replaced by the Quad 34.

The Quad 303 ran 1967 through 1985, replaced by the Quad 306.

The Quad FM3 ran 1971 through 1982, replaced by the Quad FM4.


Quad was relatively late in introducing a solid-state FM tuner.  The initial iteration of the FM3, with the TAA661B and MC1305 ICs, was still a "transitional" design, although less so than some of those that preceded it, such as the Rogers Ravensbourne and Ravensbrook, Leak Stereofetic and Sugden R21/R51.  With the 3rd iteration, CA3089 and MC1310 ICs, Quad had landed upon what became an "industry standard" basic configuration.

Cheers,

Steve

[Synchrodyne]

Would that extra power output be for a microphone mixer?

Perhaps, but with half-wave rectification and not that much smoothing I think it would need some additional work to be used for a low-noise amplifier application. 

   

Cheers,

Steve

[Craig]

There is a kit for revising the 33, from DADA for £19. That is basically replacement caps and diodes for the power supply upping it to 16V instead of 12V. That improves headroom and distortion (see douglas self's site on RIAA). It also includes replacement electrolytics for all other boards, lower noise transistors and a number of resistors to adapt the circuits to 16V, and to optionally change the gain structure.

The mod manual is downloadable from DADA if you register (they don't bombard you with spam if you do) so you can roll your own mods it you want.

Craug

[Craig]

Does anyone know what the low power DC output on pin 4 of the 33's output socket is meant to be used for? It powers the pilot light in the 33 but that's all.

The AC of that winding powers the pilot lamp. All the half-wave rectified stuff to the output socket was never used, and was in fact omitted in later production 33's. If you are changing caps on the power supply, you can just leave the half wave stuff alone, or remove the components.

Craig