The second amp board in your pictures seems to have some solder splatter around one of the eyelets in the top mid area. Shorting to anything?
If you mean around the blue and white wire, that's just electrolytic fluid that had leaked from the old output capacitor
Forgive me for calling the shots here - but the number of people who have done DADA mods who then get problems - usually without trying the amp out first.
My 303 was extremely mucky inside when I bought it. I brushed the dust off with a paintbrush. The only things I did is replace the 0,68u tantalum input cap with I honestly forget what. Maybe plastic film of the same value. And turn the big electrolytic capacitors the other way up to stop them gobbing onto the boards. I actually bought a kit from Quad with lengths of the correct colour/tracer wires and a tagstrip.
It has been going for 20 years plus since.
To give you an idea how rugged these things are, back in the mid 70's at University we used them as disco amps, worked really hard. They were fed from a homebrew mixer from Garrard SP25 decks. They had beer spilled in them, and worse, and smoke of various kinds. The cases looked like they had been in a car crash. And they just kept working. Never missed a beat, never needed repairing.
So given that there is a fair chance of a unit of whatever vintage working straight off, why run for a soldering iron first and a bunch of stuff from DADA?
My 303 was extremely mucky inside when I bought it. I brushed the dust off with a paintbrush. The only things I did is replace the 0,68u tantalum input cap with I honestly forget what. Maybe plastic film of the same value. And turn the big electrolytic capacitors the other way up to stop them gobbing onto the boards. I actually bought a kit from Quad with lengths of the correct colour/tracer wires and a tagstrip.
It has been going for 20 years plus since.
To give you an idea how rugged these things are, back in the mid 70's at University we used them as disco amps, worked really hard. They were fed from a homebrew mixer from Garrard SP25 decks. They had beer spilled in them, and worse, and smoke of various kinds. The cases looked like they had been in a car crash. And they just kept working. Never missed a beat, never needed repairing.
So given that there is a fair chance of a unit of whatever vintage working straight off, why run for a soldering iron first and a bunch of stuff from DADA?
DIYers gotta tweak - just ‘cause it ain’t broke, doesn’t mean you can’t fix it.
All fine and good - if it works after the mods. Problem is, without trying it out first to give a point of reference, you are totally lost if it then fails to work after the mods.
I'm going to shut up now 🙉
I'm going to shut up now 🙉
After owning a series of cheap Noresco “consolettes”, and a couple of early Sony receivers and speaker combos, my first serious hi-fi rig in 1973 was as Dual 701/ 33/FM3/303 combo - in that nice solid Teak sleeve - driving EPI 150s. Dayum, but half a century flies by fast. Being only in my early 20s at the time, and barely confident enough with an Unger 40W soldering iron to tin the leads on speaker wires, or make my own patch cords, I never did tweak that first Quad rig; working in a retail HiFi shop at the time, it was easier to “upgrade/taste test” by trading in - an addiction that lasted at least 3 decades, and over several career changes.
And with the input lead attached (resistor smoking)? (You’ll have to be quick!)
So I wasn't quick enough,
Amp clipped at around 4v then those resistors got so hot that one went up on flames the other the desoldered it's self and the multimeter leads pulled it from the board, did measure 2.9v ac across it before it went though
Amp clipped at around 4v then those resistors got so hot that one went up on flames the other the desoldered it's self and the multimeter leads pulled it from the board, did measure 2.9v ac across it before it went though
I would remove these input jacks or at least lift their grounding ... mabey they complete a groung loop ...
A break in the ground to the bridge rectifier causing the current return path from the output transistors to be through R115 rather than through a low impedance return wire?