Use the diagram that 337alant posted about 10 post back, this diagram has component designations, hope this helps
QUDOS - the brilliant new amplifier boards from Avondale
- Thread starter misterc6
- Start date
337alant
Negatively Biased
For starters Im not saying one resister sounds better than another!!
The welwyn RC55Y are excellent but I couldn't get them at the time I built these amps so I bought some of Tantalum resisters for any in the signal path, I may have got a little carried away in my application of them but that just my OCD !For the rest of the resisters, I first read about the Dale RN series Resisters in the Linear Audio book Vol 1 where they found them to have one of the lowest overall distortion so I figured if I am going to buy resistors buy one that have been tested and there is only pence between them and other metal films.
The first time I used them was in the paradise phono stage and I just like them
. The only thing to be aware of is they are physically larger than other similar wattage resistors so they may not fit the hole pitch in your board
Alan
Chops54
pfm Member
Les just said that T5 needed to be on the heatsink so the output stage didn't run away with itself. I suppose he has to keep it simple for non techs.
Luca
pfm Member
Sincerely, at first I planned the same modification as you suggest but after I saw the Qudos board tracks side thought that it wouldn't be working. So I added the other divertings to get the same Qudos tracks path. I'll be grateful if you will convince me that going back to the first simpler and faster solution the circuit works.
Luca
pfm Member
I had to cut two more tracks and put in two more links
Chops54, Ok! I'm willing to find the best way to get a correct-safe conversion hoping to be useful to all the DIYers.
Luca
pfm Member
NCC200 to 220.
We agree now! However you have forgotten to link the TR8 collector to the negative input and the TR10 collector.
The track between the negative input and the diode D7 lacks in the board. You have to make a bridge to link those two pads.
Chops54
pfm Member
Ive linked TR8 collector on the other side of the board. I put a link where the 100R resistor was. TR10 collector link is on the far side of the board. The link for D7 was missing on some board. You have to put your own link in. I usually bend the diode leg over but there's no components in this board.
Luca
pfm Member
Hi, not having seen the other side of the PCB it seemed to me that something was missing. Well done!
About the transistor BD237, where do you plain to put it and to lay the flying leads? Under or over the boards and under or inside the U heatsink? I have an idea but I'm interested in knowing your method and compare it with mine.
Chops54
pfm Member
Hi Luca, I was going to run flying leads from the BD237 to the board. It's a bit of a stretch and that 220nf cap might get in the way but I'll have to work on it. I don't like having flying leads on the component side and I'm thinking you may have a better idea?
I've been looking at the mods I've done to this board and thinking how I could do it better. I have another used board to practise on and hopefully I can do it a bit nicer this time.
I've been looking at the mods I've done to this board and thinking how I could do it better. I have another used board to practise on and hopefully I can do it a bit nicer this time.
Luca
pfm Member
To get satisfaction, in my works I always looking for absolute tidy and neat solutions. As you, I don't like having flying leads casually passing throught the electronic components. The board is full of parts and the passage through all them is an unaesthetic efforty slalom. So I'm thinking for a solution under the board but this needs a different position for TR5. I'd make a little bigger heatsink to fix the transistor in an alternative point close and between TR9 and TR10. To be clear I have to do a drawing and post it.
Chops54
pfm Member
Ok, I think this is a bit tidier Luca.
On the component side you can see the link across the 100R resistor that puts the collector of TR8 to the negative rail. I've put D7 in so I could bend over the leg to make the link to the same rail. Collector of T10 goes to the negative rail from its other mounting bolt.This time I took the base of TR10 straight to TR8 emitter. That solder tack halfway down the track is just to hold the link in place. You can see the two holes where D6 used to be ( no longer required) If those links are painted green they will be barely noticeable.
As for the BD237, Im thinking of drilling a hole just to the side of the + sign and bringing the flying leads up through there. Maybe we could put the 220nf cap underneath the board and put hole around there somewhere for the leads to come up?
On the component side you can see the link across the 100R resistor that puts the collector of TR8 to the negative rail. I've put D7 in so I could bend over the leg to make the link to the same rail. Collector of T10 goes to the negative rail from its other mounting bolt.This time I took the base of TR10 straight to TR8 emitter. That solder tack halfway down the track is just to hold the link in place. You can see the two holes where D6 used to be ( no longer required) If those links are painted green they will be barely noticeable.
As for the BD237, Im thinking of drilling a hole just to the side of the + sign and bringing the flying leads up through there. Maybe we could put the 220nf cap underneath the board and put hole around there somewhere for the leads to come up?
James Evans
Bedroom Bodger
Thanks for posting those Si. I have a pair of bare 200 boards I was contemplating doing this to at some point so this will make a handy reference.
I've just finished re-housing my 220 into a new case, all the wiring done. If using VBE for front end can someone remind me best way of measuring bias? I was thinking multimeter in +ve line of output stage and add on about 20mA?
I've just finished re-housing my 220 into a new case, all the wiring done. If using VBE for front end can someone remind me best way of measuring bias? I was thinking multimeter in +ve line of output stage and add on about 20mA?
James Evans
Bedroom Bodger
N+1 applies to DVM ownership...
Luca
pfm Member
NCC 200 conversion: "the heatsink".
I’ve found a pair of solutions to link the TR5 (BD237) transistor to the heat sink.
The first is very easy and need of a bigger heatsink. The Avondale modules have a 35 x 35 mm U profile while I use a 40 x 40. The first advantage is the latter is much easier to find and having a little more surface is a bit more dissipative. It also allows to achieve an 8mm gap between the edge of the board and the core of the aluminum profile which is what we need.
Heatsink LV by Luca B, on Flickr
Along this gap is possible to drill an hole or better mill a slot where the flying leads and the transistor legs can joint togheter. Their isolation by heatsrink sleeves is strongly recommended. I hope the following rendering will help ...
Heatsink3 by Luca B, on Flickr
Heatsink1 by Luca B, on Flickr
I’ve found a pair of solutions to link the TR5 (BD237) transistor to the heat sink.
The first is very easy and need of a bigger heatsink. The Avondale modules have a 35 x 35 mm U profile while I use a 40 x 40. The first advantage is the latter is much easier to find and having a little more surface is a bit more dissipative. It also allows to achieve an 8mm gap between the edge of the board and the core of the aluminum profile which is what we need.
Heatsink LV by Luca B, on FlickrAlong this gap is possible to drill an hole or better mill a slot where the flying leads and the transistor legs can joint togheter. Their isolation by heatsrink sleeves is strongly recommended. I hope the following rendering will help ...
Heatsink3 by Luca B, on FlickrHeatsink1 by Luca B, on Flickr
Chops54
pfm Member
Working NCC200 boards don't seem to fetch a lot atm being overshadowed by the newer, better Qudos. It makes good sense then to mod the old boards.