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Quad 303 rebuild starting Circuit board routing needed.

MrIgotNomoney

MrIgotNomoney

Well-Known Member
Guys
I'm starting a Quad 303 rebuild, I saved 2 303's from being parted out.
I have been hanging on to these guys for a couple years at least, so figured it was time to get them fixed now that winter is here.
Both are missing all 3 of the circuit boards.
I have bought 2 sets of blank boards from Joost at Quad spot.
quadrevisionspot.blogspot.com

The boards are nice quality, but are not drilled or routed.
I did get the drilling done, but I need to get slots routed in the circuit boards so they can be mounted in the chassis.
Any ideas out there who or what company could do this kind of work????

Also has anyone out there worked on the Quad 303 amp ?
Im looking for tips/ ideas.
Im looking for replacement transistors, going Onsemi MJ15003 for outputs and MJ802 for the power supply regulator.
I have BC441/461 for the driver transistors.
All resistors and small caps I can get from Digikey, or locally.

I have a 303 that is original, except for new caps and it is a sweet little amp even if it looks like a toaster.

bob
 
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Illecillawae
Thanks man, just put in an order to net audio for upgrade parts. thanks man
Also got an order into digikey for resistors.
I have new circuit borads, drilled and ready to go.
So hopefully Ill have all the small parts in a week or so, right in time for the Xmas holiday.

bob
 
Illecillewae -- you are missing the "t" on the end of your nick. :D A truly memorable experience standing on top of that glacier, years ago. :thmbsp: Sorry, totally OT, but that brought back some cool memories.
 
Yes I know the "t" is missing. Since I started computing I am on my 15 or 16th keyboard and none of the damn things can spell!!

Best of the season to one and all.

RGK, Calgary
 
Guys a few photos of the almost complete circuit boards for 1 Quad 303
I was waiting on a couple input caps and a resistor.
I have finished all 3 boards and installed them in the 303.
First fire up she was within range on with the B+ voltage and bias. WOW !!!
Plays like a fiend.
Blank circuit boards and some small parts from Joost at Quad spot.
Im using computer grade power supply 2x 2600uf and output caps are 10,000uf.
High current inductor,1% or 5%film caps, I did match the transistors,
Output transistors are Onsemi, small signal transistors are Fairchild, driver transistors are National Semiconductor.
bob
POWER SUPPLY REGULATOR
DSC_7315.jpg

AMPLIFIER BOARD
DSC_7322.jpg

AMPLIFIER BOARD
DSC_7350.jpg
 
Guys
Finnished the First Quad 303 and fired it up.
No problems what so ever ! It lives and I didnt let out any magic smoke.
After about 30 minutes checked and tweeked voltages and bias current.
So far she has been totally stable.
bob
 
Quad 303

Radfordman said:
What did it sound like?
Click to expand...
Hello
Thanks, I have to say the little Quad sounds great.
Along with the total rebuild I did change the power supply caps and coupling caps for the output stage, so she is totally new.
The sound is totally clean, excellent detail, very good bass, it surprises my musician friends just how good it does sound.

The one thing about the 303's sound is, I dont think it has the typical solid state sound of the time. I hear a refined presentation, better detail and clarity than my Perreaux 1150b.
Actually the 303 is on of my favorite amplifiers of all, and as new no doubt about it.

bob
 
Hi

Nice work there. I have two sets 33/303 resting and doing nothing. I bought them years ago, got them checked over and packed them away, never used. Waiting now for the firest long weekend to feed them some ac with a 100W lightbulb first.

tripod
 
MrIgotNomoney said:
Hello
Thanks, I have to say the little Quad sounds great.
Along with the total rebuild I did change the power supply caps and coupling caps for the output stage, so she is totally new.
The sound is totally clean, excellent detail, very good bass, it surprises my musician friends just how good it does sound.

The one thing about the 303's sound is, I dont think it has the typical solid state sound of the time. I hear a refined presentation, better detail and clarity than my Perreaux 1150b.
Actually the 303 is on of my favorite amplifiers of all, and as new no doubt about it.

bob
Click to expand...

Excellent, that's what I like to hear. There are probably many 303's around unserviced (for 30 years or so) and sounding OK, however after a good service the sound is quite excellent.

I have four 303's two bought in recent years, the other two bought in the 70's. All were second hand and have been uterly reliable. Only recently were the output and power supply capacitors replaced. I upped the output capacitors to 10, 000 uF just in case I want to drive low(ish) impedance speakers. In may help the bass in such circumstances.

I prefer the 303 to my Quad 405-2 that has burr Brown opp amps.

However, I'm afraid that the 303 is beaten by my tube Radford STA25 III, in fact all amps I have had are beaten by this one, so its no reflection on the 303.

My only grumbles about the 303 can be fixed easily.

1/ Horrible Din input socket (needs phono sockets)

2/ No on off switch (could be fitted where fuse is on front panel

3/ Possibly nice to have an input volume control

I hate to drill and modify the front panel

I know Net Audio do a new front panel to cater for some of these things.

As they say, the BBC used Quad 303 and so did Pink Floyd!

One question Mr Igotnomoney, what preamp do you use with the Quad 303?
 
Last edited:
Tripod said:
Hi

Nice work there. I have two sets 33/303 resting and doing nothing. I bought them years ago, got them checked over and packed them away, never used. Waiting now for the firest long weekend to feed them some ac with a 100W lightbulb first.

tripod
Click to expand...

Hi Tripod, I guess that you know, its worth physically checking the output and supply capacitors before firing up after storage. On older production they are mounted connectors downwards and if they leak, the electrolyte goes all over the driver boards, with obvious consequences.

Later production 303's have the capacitors mounted conectors upwards, so if caps leak, less likely for electrolyte to get on to driver boards.

Stupidly, I did not change mine round, mainly because the wires to the capacitors have to be lengthened.
 
I've had three of these things. I worked on all of them when I was learning and kinda screwed it up. On reflection I was a total idiot back then and know how to do it now.
Only thing is that I don't have a 303 any more. Since all you guys seem to have truck-loads of them, what to send one my way? I can pay freight or whatever. I just want to restore one properly, especially if Mr. Igot reckons they're better than the 1150, which is one of my favourite amps!

Igot, where did you find the Perreaux? I didn't think any 1150's made it to the states...
 
Quad 303

Deczor said:
I've had three of these things. I worked on all of them when I was learning and kinda screwed it up. On reflection I was a total idiot back then and know how to do it now.
Only thing is that I don't have a 303 any more. Since all you guys seem to have truck-loads of them, what to send one my way? I can pay freight or whatever. I just want to restore one properly, especially if Mr. Igot reckons they're better than the 1150, which is one of my favourite amps!

Igot, where did you find the Perreaux? I didn't think any 1150's made it to the states...
Click to expand...


Deczor
Hi,
man I love the 303, hard to beat little amp.
Ok on the Perreaux, I found mine at a swap meet a few years ago, And I was blown away with the sound, the Perreaux is hard to beat. I'm not saying the Quad is a better amp, just different. The Perreaux is so smooth sounding it seems a little rolled off, but in fact is not at all.
What I notice between the Quad and 1150b was the Quad was a little more forward, but not harsh or grainy at all, just a little extra bite.

bob
 
Quad 303

Radfordman said:
Excellent, that's what I like to hear. There are probably many 303's around unserviced (for 30 years or so) and sounding OK, however after a good service the sound is quite excellent.

I have four 303's two bought in recent years, the other two bought in the 70's. All were second hand and have been uterly reliable. Only recently were the output and power supply capacitors replaced. I upped the output capacitors to 10, 000 uF just in case I want to drive low(ish) impedance speakers. In may help the bass in such circumstances.

I prefer the 303 to my Quad 405-2 that has burr Brown opp amps.

However, I'm afraid that the 303 is beaten by my tube Radford STA25 III, in fact all amps I have had are beaten by this one, so its no reflection on the 303.

My only grumbles about the 303 can be fixed easily.

1/ Horrible Din input socket (needs phono sockets)

2/ No on off switch (could be fitted where fuse is on front panel

3/ Possibly nice to have an input volume control

I hate to drill and modify the front panel

I know Net Audio do a new front panel to cater for some of these things.

As they say, the BBC used Quad 303 and so did Pink Floyd!

One question Mr Igotnomoney, what preamp do you use with the Quad 303?
Click to expand...

Radfordman
I agree, I have a pair of Quad 405's both rebuilt, with new opamps, they sound pretty good, but the 303 I think bests them. I agree the din input is a pain, the high gain on the 303 also makes matching them up a hassle, I run my 303's from a Music Reference RM5 tube pre.
I also thought about the net audio front panel also, but didn't want to spend the money. I did go for the constant current diodes, I did notice a difference, compared to a totally stock 303. I agree on the 10,000 uf caps for the output, definitely did beef up the bass.

The 303 is just one hell of a good little amp, I never get tired of listening to it, nothing fatiguing. my buddys swear there is a tube in there....

bob
 
Only thing missing from that is the pot (or volume control on the input) and perhaps retaining the Din socket as well for use with original signal lead.
 
Hello
One thing I forgot to mention is I used the original Quad Spot boards, they do allow for input sensitivity adjustment. This works out pretty well, but I think the best sound is with the original specification setting.
bob
 
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