Quad 303S Power Amplifier

Quad 303S Power Amplifier.

Serialnumber: 26640

I am a retired Electronics Engineer former Radiomechanic also , doing repairs as a hobby. This is NOT A BUISNESS !

This UNIT i traded against some vacuum tubes . It has been serviced/recapped by previous owners at some point but i don not know if it was the individual i dealt with.

I dissasembled it to check on things just to see what has been done.
What i did to the unit :
1. I replaced one of the power supply capacitors , the RED one in the pictures it was an odd high voltage low capacity type and i replaced it with one fitting the others and all are now 4700uf/100V types.
2. Resoldered a few things.
3. Cleaned a bit with the vacuum cleaner.
4. Adjusted BIAS/Vcc and OFFSET.
5. Cleaned all DIN SOCKETS and tightened them.
6. Final testing under FULL LOAD 8ohm and verified THD , distortion , levels acc. to SPEC.
It performs really well somewhat better than spec. Added a picture showing THD at 49W/8ohm in one of the channels , THD=0.01% . Both channels are similiar. The harmonic content you see is typical for QUASI Complementary outputs although this one is a triplet type it still only uses NPN types as the output.
7. At some point in its life both outputs have been serviced , emitter transistors and output indictors in both channels seem to have been replaced and PCB underneath revelas they onec were very hot. So i checked the output transistors and as far as i can see all transistors seem of GENUINE origin so repairs must have been at a time these were available. Voltage regulator has also seen some repairs .

Cosmetics :
When i received it it had seen some transport damage , one of the heatsink finns was bend. A typical problem when pacakaging is insufficient. I managed to straighten it out almost completely but did'nt dare to keep going since i dont have tooling for that. However it is almost straight again. You can see the cracking paint on the corner in question.
In general the internal and externals reveils that the unit at some point in its life has seen some humid storage , Rust on steel parts and transformer core. Corosion on aluminium parts and flacking paint here and there.
So if you want a MINT unit THIS IS NOT THE ONE although in my mind it is decent enough to what i have seen before. At least faceplate is not butchered :)

TERMS OF THIS AUCTION , PLEASE READ BEFORE YOU BID !

Payment : Since i have received messages asking for rather LONG DELAYED PAYMENTS i have to state ; I APPRECIATE a payment within 24h , i accept max 3 days . To those who may still ask these questions , i WONT ANSWER ANYMORE AND YOUR PROFILE IS BLOCKED .

SHIPPING : I use TRADERA ONLY ! Which means i can only chose BRING as courier. They have strict size and weight conditions i have to meet which is why i PACK before i make the ADD so the shipping cost shown by TRADERA is the CORRECT ONE !

I suffer from a severe chronical STRESS condition which is why i take every measure to avoid any stress assosiated whit these auctions.

IF YOU CHOSE TO BID ON MY AUCTIONS YOU CONFIRM AND ACCEPT these TERMS :

1. My packaging is evaluated sufficient to avoid any shipping damages , you see my packaging on the pictures attached.

2. In the unlikely event of shipping damage it is your own responsibility to forward any claims towards the shipping company and document the damage . I just cannot assist . So when you receive the package start taking pictures BEFORE any unpacking and as you unpack , this way you have the documentation you need.

3. There is NO RETURN and NO WARRANTY involved. I have done everything possible to detect any issues and correct failures. With VINTAGE HiFi it is to be expected that failures can surface ANY TIME and equipment requires periodic maintenance. Regardless of how many components i have replaced the majority are still vintage . It is no different than with a VETERAN CAR !