I have recently purchased a quad 33 and 303 in original condition.
The only problem is that i am not getting right channel sound.
I have ruled out cabling issues.
I am connecting to tape replay using an rca cable to DIN which i connect to my laptop.
I have tried all stereo left and right buttons. but simply not getting audio from the right channel on the 303. The speakers work.
I am going to confirm soon to rule out the 33 by measuring the output from the 4 pin DIN output cable.
I've opened up the 303 and the only obvious issue i can see visually is the C104 cap on the left driver is blown (as in the top casing of the capacitor is gone and i see the yellow internals) but the left channel works. the right channel driver components look fine. everything else also looks fine visually
Please could you provide a fault finding instruction to identify the fault causing the right channel not to work?
any help would be appreciated
The only problem is that i am not getting right channel sound.
I have ruled out cabling issues.
I am connecting to tape replay using an rca cable to DIN which i connect to my laptop.
I have tried all stereo left and right buttons. but simply not getting audio from the right channel on the 303. The speakers work.
I am going to confirm soon to rule out the 33 by measuring the output from the 4 pin DIN output cable.
I've opened up the 303 and the only obvious issue i can see visually is the C104 cap on the left driver is blown (as in the top casing of the capacitor is gone and i see the yellow internals) but the left channel works. the right channel driver components look fine. everything else also looks fine visually
Please could you provide a fault finding instruction to identify the fault causing the right channel not to work?
any help would be appreciated
I think the first step should be to run the power amp on its own, preferably with a signal generator. Narrow down the battle field, there's too many variables.
I guess you swapped the speakers to rule that out.
Jan
I guess you swapped the speakers to rule that out.
Jan
Hi Jan,
yes speakers were swapped to rule out.
Good suggestion i tried the 303 first and to my surprise the right channel does work and has significantly better output than the left channel.
could it be because of the C104 that i noticed is blown on the left channel driver?
this informs me the quad 33 is not outputting the right channel as I've tested the cables for continuity.
I will open up the 33 and report back.
Not sure what you mean by better output, and I don´t know where in the circuit that C104 is but if it is obviously blown I would quickly replace it.
No telling what havoc it could wreak next when left to its devices!
Jan
No telling what havoc it could wreak next when left to its devices!
Jan
C104 provides the time constant for the DC servo. Without it, the voltage at the top of RV100 will try to hold the whole signal steady, instead of just what survives being shunted by C104, which is just the subsonics.
I would change C100, C101, C104, and C106 in both channels before doing anything else. C106 needs a 63V rating, the others only 16V or less.
In the 33, first check that all boards are correctly seated.
EJP
I would change C100, C101, C104, and C106 in both channels before doing anything else. C106 needs a 63V rating, the others only 16V or less.
In the 33, first check that all boards are correctly seated.
EJP
They are all electrolytics and 50 years old.
But yes I do like soldering :-|
But yes I do like soldering :-|
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Really appreciate the advice.
Jan, left channel sounds significantly attenuated compared to the right channel.
EJP, I was actually reading your comments on a YouTube video comparing Frequency response post cap changes on the 303. I was wondering how do I get in touch with this person. Excellent!
Jan, left channel sounds significantly attenuated compared to the right channel.
EJP, I was actually reading your comments on a YouTube video comparing Frequency response post cap changes on the 303. I was wondering how do I get in touch with this person. Excellent!
Left channel attenuation could be the balance slider disconnected. The fork thing breaks. You can see by looking down from the top whether moving the balance control really rotates the pot or not.
Otherwise check/replace C405 on the 33 amplifier boards, another electrolytic to assuage my love of soldering ;-) This is the emitter bypass of the gain transistor, and if it opens the gain goes down a few dB.
I use 22uF for C104 in the 303, and 1uF film for C100. This extends the bass a little.
Otherwise check/replace C405 on the 33 amplifier boards, another electrolytic to assuage my love of soldering ;-) This is the emitter bypass of the gain transistor, and if it opens the gain goes down a few dB.
I use 22uF for C104 in the 303, and 1uF film for C100. This extends the bass a little.
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