Hi I wondered if any one has any advice for trouble shooting my 34 pre amp that is making a crackling noise in one channel?
Seems to improve as the amp warms up.
I tried disconnecting the power amp (Quad 405/2) and the noise goes away so am assuming its to do with the 34.
Theres also popping/crackling noises when switching inputs.
Any advice appreciated, have some limited technical abilities 😁 and would like to attempt my own repair.
Seems to improve as the amp warms up.
I tried disconnecting the power amp (Quad 405/2) and the noise goes away so am assuming its to do with the 34.
Theres also popping/crackling noises when switching inputs.
Any advice appreciated, have some limited technical abilities 😁 and would like to attempt my own repair.
First carefully clean all the switches/pots/contacts. Some of the noise then will likely be gone.
Now determine if the volume control reduces the remaining noise.
It's possible that some electrolytic capacitors are leaking, or there are bad connections, etc.
http://www.meridian-audio.info/public/quad_34_service_data_manual[1582].pdf
CAIG DeoxIT D5S-6 Spray 5 oz. with Perfect Straw
Now determine if the volume control reduces the remaining noise.
It's possible that some electrolytic capacitors are leaking, or there are bad connections, etc.
http://www.meridian-audio.info/public/quad_34_service_data_manual[1582].pdf
CAIG DeoxIT D5S-6 Spray 5 oz. with Perfect Straw
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"Seems to improve with the amp warming up"--- sound like a high resistance soldered joint --somewhere.
Once heated the resistance drops.
Once heated the resistance drops.
Resolder the six joints for the volume pot. Remove all the old solder and redo. Ditto the audio connectors where they enter rthe PCB.
Take care with manipulating Quad 34 controls. They are unique and virtually irreplaceable components with intricate but flawed and fragile designs. The rotary tone switches are an utter nightmare to repair since parts are unobtanium unless you can salvage them from a wreck. The link is to an article with useful illustrations and comments on the popular range of original Quad products, including the Quad 34.
Some comments appear to be personal views that we may well disagree with but at least the facts and pics are there: Quad Refurbishing
Some comments appear to be personal views that we may well disagree with but at least the facts and pics are there: Quad Refurbishing
Thanks I will have a go at cleaning the the switches VERY carefully and then see what noise is left.
In my limited experience and from discussions in previous Quad 34 repair threads here, the most common electrical problem with them is actually with the PCB itself. Under the green lacquer, corrosion of the copper foil typically goes on slowly for many years and it isn't that easy to see without strong lighting and perhaps washing away any accumulated grime with isopropyl alcohol or hot soapy water and drying the whole thing thoroughly.
Over many years, the electrolytic capacitors seem to leak tiny amounts of electrolyte which aren't volatile, so they seep over the PCB surface and down through the many holes in the PCB then laterally, between the substrate, foil and lacquer layers. It's evidenced by darker blotches on the copper foil surface, though a bad example shown me by tech, had even bubbled up through the coating, leaving a powdery, greenish mass and needless to say, the sound was crackly in one channel and dead in the other. Somebody at Quad or their PCB maker, was ill-informed back in the day because few other manufacturers globally, seem to have had such a problem.
Over many years, the electrolytic capacitors seem to leak tiny amounts of electrolyte which aren't volatile, so they seep over the PCB surface and down through the many holes in the PCB then laterally, between the substrate, foil and lacquer layers. It's evidenced by darker blotches on the copper foil surface, though a bad example shown me by tech, had even bubbled up through the coating, leaving a powdery, greenish mass and needless to say, the sound was crackly in one channel and dead in the other. Somebody at Quad or their PCB maker, was ill-informed back in the day because few other manufacturers globally, seem to have had such a problem.
I'm restoring a 34 and it has the very same issue. First few minutes it's clean, then the left channel start cracking lightly and it becomes worse as the unit warms up. Many traces are indeed corroded.... I wonder if you ever managed to fix that and what was the part causing it?