Quad 303 mods

[mikes08]

More pictures...

[Pcspike]

Originally Posted by mikes08

More pictures...

Mike, that's great, exactly what I wanted to see. Thanks for taking the time, it's appreciated.

Dave

[Pcspike]

Originally Posted by Radio Wrangler

While fixing amplifiers in general, there is one little aspect that you don't want to miss, where you've picked up enough knowledge of the technologies and circuits, throw the whole damned thing on the floor and declare "I could do better than that!"

A remarkable number of firms began this way.

David

I'll keep that in mind

[Pcspike]

Originally Posted by nutteronthebus

If you do run into problems I am only in Glossop and may be able to help ( waiting for a heart bypass at the moment ) so it is a timing issue when I am available

Dave

That's a very kind offer, thank you. I do hope that the op goes well and that you will soon be running about again

[Pcspike]

Originally Posted by Whaam68

As others have said take good clear pics to refer to before disassembling anything. With the big can caps when replacing those just ensure you match the polarity (marked on the caps "+" by the terminal and "-" a stripe down the side. So the wire that went to + on the old cap goes to + on the replacement cap, etc. If you update the wiring to the caps the same principle applies. As other Mike said it's likely you'll have to update the mounting clips as the new caps will have a smaller diameter. Either pad out the existing clips or buy new clips and re drill new mounting holes. IF your 303 is an early one with the terminal end of the caps facing the PCB some people choose to reorient them as quad did on later serial numbers (although with modern cap construction techniques I'm not entirely sure that's really necessary....but I did it anyway). The extra wiring in the kit is probably to enable people that need to to do that. The colour of the wiring doesn't make any difference at all as long as the gauge (thickness) of the core of the wire is roughly equivalent.
Mike

Thanks for that

[mikes08]

I will correct one comment i made earlier - the yellow leads are used to connect from the transformer to the rectifier not the caps as i said earlier. Just follow the instructions on the 303 upgrade instructions and you won't go wrong though you may find they send instructions though this would not be their normal format as all appear to be downloads. It is up to you if you solder directly onto the pins or not but i used the crimp connectors as i has some and you can take the boards out if you ever need to more easily. I think the pins are silver plated and the crimps possibly ally but will see in time if there is any reaction between metals.
Shrink wrap if you feel inclined but again i only did this as i had some.
I have some more pics to follow.

[mikes08]

More pictures ........

[mikes08]

and some more.......

[mikes08]

and don't forget to set you bias current when done - again follow the instructions. Allow the amp to warm up a bit but easy enough - again use a small piece of wood to keep the boards away from the chassis....

[Pcspike]

Originally Posted by mikes08

The yellow wires are indeed used to connect up the capacitors to the rectifier though if you buy the 303 upgrade kit they supply red and blue. If you follow the instructions from the 303 upgrade it is simple enough and you might want to swap out the yellow wires and use as above. They might supply different from the website pictures and may include instructions with it - i bought mine second hand so not sure.
The boards are a straight swap but rather than solder the wires onto the pins you might want to get some connectors to solder onto the amp wires that slip on the pins to make a neat install - they may supply these in the kit also? I had some spares so this is what i did.
I can post some pictures of my installation if it helps and if your get stuck can help.
Once in you need to set quiescent current and again instructions in the 303 upgrade details. Do use a piece of wood to rest the boards on and keep away from the chassis. Just take notes as you remove the old boards or take some pictures.
I used the original mounting rings for the main caps but the capacitors supplied were smaller in diameter. I bought some 2mm high density sponge from e bay and cut a small strip (about 20-25mm wide) and glued it round each capacitor to 'pad' them out.

Thanks Mike, I like that idea of using connectors to fit onto the pins. I'll source some after I get my boards.
I've been trying to think of a method of extending the terminals of the snap-in type capacitors that could be attached or soldered so as to have a larger area to solder the wires to like the original caps, perhaps there's already a method out there that I've not yet come across.

[mikes08]

I've been trying to think of a method of extending the terminals of the snap-in type capacitors that could be attached or soldered so as to have a larger area to solder the wires to like the original caps, perhaps there's already a method out there that I've not yet come across

They are not too bad to do - just tin the terminals and the wires hold together and introduce the iron - job done. If you have any shrink wrap......

[Pcspike]

Originally Posted by mikes08

The boards are a straight swap but rather than solder the wires onto the pins you might want to get some connectors to solder onto the amp wires that slip on the pins to make a neat install - they may supply these in the kit also? I had some spares so this is what i did.

Regarding the connectors, any pointers as to where I can purchase them. Been looking online but can't see anything similar to what you have used. Thanks

[mikes08]

https://shop.dadaelectronics.eu/prin...re-connectors/

https://shop.dadaelectronics.eu/13mm...108463125.html


Dada sell the pins and tags so i would go there - bit of a faff ordering/paying as you know but not too difficult and i think your board will be populated already with the pins looking at the online picture? - so you just need the tags. They may even supply these in the kit too but if not, you can order them there and don't forget the two connectors away from the main side of the amp harness for each board.

[Pcspike]

Originally Posted by mikes08

https://shop.dadaelectronics.eu/prin...re-connectors/

https://shop.dadaelectronics.eu/13mm...108463125.html


Dada sell the pins and tags so i would go there - bit of a faff ordering/paying as you know but not too difficult and i think your board will be populated already with the pins looking at the online picture? - so you just need the tags. They may even supply these in the kit too but if not, you can order them there and don't forget the two connectors away from the main side of the amp harness for each board.

OK and thanks (again)

[nutteronthebus]

I have just found these on ebay https://www.ebay.co.uk/itm/134231976...ee24%7Ciid%3A1 mod delete if not allowed

Dave