quad 33 comments please

[j baldam]

Hi,
my quad 33 pre has arrived.
After a bit of fiddling I managed to get it working on both chanels, radio2 only seems to work on 1. Radio 1 is fine.

Could any 33 owners please comment about the innards of this particular amp as I was going to mod it but it seems someone may have got there first.

Peeking inside I notice that all control pots are green plastic, all the pics I've seen show larger metal pots.

The volume pot does not have the facility to switch on and off, the amp is on all the time.

I've pictured the two main boards and they seem different to standard as does the power supply board. And the power supply wiring.

http://i1095.photobucket.com/albums/i464/Jbaldam/DSCF1911.jpg

http://i1095.photobucket.com/albums/i464/Jbaldam/DSCF1914.jpg

There is a liberal application of some silicone like substance over most components and boards

 

[tinitus]

I dont know, but could it have been completely rebuilt ?

 

[j baldam]

Hi, thanks.
If all the pots are non standard then someone has taken a lot of trouble.

 

[Huntingdon 361]

It looks like:

1) All the pots have been replaced.
2) Most of the electrolytics have been replaced.
3) Some of the film capacitors on the M12017 pcbs are original, some replaced. The green box capacitors can certainly be original.
4) The mains input wiring looks non-original, and there is also some new wiring from the power supply board to the main pcb.

I am mystified as to why anyone would want to put that sealer/glue on the boards.

The Quad 33 is pretty straightforward to work on and you should have no trouble dealing with any problems. Report back if you're stuck on anything.

 

[dennusch]

Every resistor, capacitor and pot seems to be non-standard to me.

 

[Tekko]

Seems like some kinda conformal coating.

 

[j baldam]

Hi, thanks,
It certainly looks rebuilt from the ground up.
Could anyone please identify this brown capacitor, it has a capital M in a circle, is it Motorola?

An externally hosted image should be here but it was not working when we last tested it.

 

[Tajzmaj]

I think it's Panasonic......
Cheers

 

[j baldam]

Hi I think your right, thanks,
I've found these but I can't find 22uf 250v, would anyone know of a supplier please.
4 PCS. Panasonic MPET Capacitor 0.22uF / 10% / 100V | eBay

 

[Huntingdon 361]

but I can't find 22uf 250v

Where do you need 22µ 250v?

 

[j baldam]

hi, lost in translation, it's 2.2 uf.

I sent the pics to DaDa europe and he reckons that although a lot has been replaced I would be better off following their kit values.
I will be using cd into the tape board so there won't be a lot to do.
Power supply increase and changes to the tape board.

 

[j baldam]

hi, I have had some interesting advice from DaDa Australia.
He pointed me towards a mod on the power supply.
Basicly you remove all parts from the power board except the transformer.

Two diodes are added for rectification.
A 12v reg is fitted and a 2200uf cap and 100uf cap and a link across c504.


I have done this and the results with CD into the tape board are outstanding.
This has impessed me so much that I have called it a day with modding.

I am now rediscovering my old CD's.

Link here
Quad Spot

An externally hosted image should be here but it was not working when we last tested it.

 

[sbrads]

I am mystified as to why anyone would want to put that sealer/glue on the boards.

Perhaps whoever rebuilt it was used to military PCB construction methods. If it's the real deal you will be able to solder/unsolder through it and heat will soften it enough to lift components.

 

[j baldam]

When doing the mods I have removed some "glued "parts.
It looks like all the new bits were glued into place, then soldered.

I can only think he wanted the board assembled before soldering in one go

 

[vacuphile]

As sbrads menetioned, glueing stuff to the PCB is what is done in military/aviation (at least they used to do it, don't know if it is still done). Some PCBs were even casted into epoxy, a one way only solution. It makes sense for electronics in a high vibration environment, but I don't think it has benefits for a pre-amp.

 

[sbrads]

Glueing is still done in military gear, but usually it's only big wobbly components that get bonded down, all the small stuff just gets conformally coated (like a varnish that you can solder through for repair work). If there's a heatplane (a flat metal plate with holes for component leads bonded to the topside of the pcb), then ICs and 'laying down' components may get a heat transfer compound under them, usually a liquid that sets, for cooler running.