I just got a dead CX-800 pre amp I hoped to repair. it does not turn on.
there are no fuses anywhere that I can see
120 goes into the transformer but nothing come out
input leads for the transformer shows no resistance at all, as in completely open it seems
lifted up transformer to look underneath, it is epoxy encased
outputs are
red black red for 23 gnd 23V
orange orange 14V
I am wondering why I can find no fuses at all (even on the schematic) and the big question, what can I use in place of this transformer
there are no fuses anywhere that I can see
120 goes into the transformer but nothing come out
input leads for the transformer shows no resistance at all, as in completely open it seems
lifted up transformer to look underneath, it is epoxy encased
outputs are
red black red for 23 gnd 23V
orange orange 14V
I am wondering why I can find no fuses at all (even on the schematic) and the big question, what can I use in place of this transformer
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Are you checking for continuity across AC1 and AC2 on the board?
If that reads "open" then it's possible that an internal fuse in the transformer is bad.
Which means a replacement is needed.
If the fuse blew, then I'd check around the PS for a possible overloading condition which may have caused the transformer to overheat and fail.
As for finding a replacement, good luck.
If that reads "open" then it's possible that an internal fuse in the transformer is bad.
Which means a replacement is needed.
If the fuse blew, then I'd check around the PS for a possible overloading condition which may have caused the transformer to overheat and fail.
As for finding a replacement, good luck.
Yes, AC1/AC2 test open
when I looked at the bottom of the transformer I did not see a user replaceable fuse
is there a special trick to accessing it? the transformer is epoxy encased
when I looked at the bottom of the transformer I did not see a user replaceable fuse
is there a special trick to accessing it? the transformer is epoxy encased
You're crap out of luck, sorry.
Replacment of the transformer is as I mentioned, the only option.
Primary winding gone open, or secondaries?
Remove from circuit and check the mains winding again, meaning meter direct to transformer leads or terminals.
And both secondary gone means big problem, in most amps the lower volts are for the tuner / pre amp / selector, and the higher voltage for the output section.
To find the fault and repair it, with a new transformer, and replacing faulty parts, will be tedious and expensive.
Your decision.
Remove from circuit and check the mains winding again, meaning meter direct to transformer leads or terminals.
And both secondary gone means big problem, in most amps the lower volts are for the tuner / pre amp / selector, and the higher voltage for the output section.
To find the fault and repair it, with a new transformer, and replacing faulty parts, will be tedious and expensive.
Your decision.
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Transformer, new, here, 220V mains, 250 mA / 14 V, and 1A 28V, would be north of $25.
Shipping would be double that, and India is cheap.
See if Chinese suppliers can sell you one.
If it is an amp, calculate secondary amps, add 20% for safety.
Figure about $200 as a thumb rule cost, with your free labor, for total repair.
The fault usually is on one winding, though it may be a single one with two taps.
Shipping would be double that, and India is cheap.
See if Chinese suppliers can sell you one.
If it is an amp, calculate secondary amps, add 20% for safety.
Figure about $200 as a thumb rule cost, with your free labor, for total repair.
The fault usually is on one winding, though it may be a single one with two taps.
Try gently to check near the terminals, if you are lucky the joint of windings to lead might be open. That is rare, with Japanese quality.
Those ratings mean you could use similar transformers, finding one will be easier from a maker in the Far East.
Those ratings mean you could use similar transformers, finding one will be easier from a maker in the Far East.
the primary winding is open, I am testing at the lead wires to the transformer itself.
if I can't get or make a transformer replacement for around $25 I will just part out the set I will use it as backup parts to my working CX-800 although I would love to get it working.
this place has the transformer but the price is too high by about $375. the whole pre-amp is not worth $398
https://spwindustrial.com/new-genuine-yamaha-part-xe489002-power-transformer-cx800-u/
if I can't get or make a transformer replacement for around $25 I will just part out the set I will use it as backup parts to my working CX-800 although I would love to get it working.
this place has the transformer but the price is too high by about $375. the whole pre-amp is not worth $398
https://spwindustrial.com/new-genuine-yamaha-part-xe489002-power-transformer-cx800-u/
Try a Chinese supplier.
Or use it as a parts donor, the primary open is a normal fault compared to secondary open.
Some Kenwood sets also use similar windings.
So instead of looking for Yamaha part, look for the similar rated generic transformer, much cheaper.
Or use it as a parts donor, the primary open is a normal fault compared to secondary open.
Some Kenwood sets also use similar windings.
So instead of looking for Yamaha part, look for the similar rated generic transformer, much cheaper.
It is a pre, right?
Put a 24V SMPS, and another 12V SMPS or a 317 / 7812 based drop circuit to get 12V from the 24V unit, feed those to the existing secondary inputs on the PCB. That will help reduce noise from SMPS, and regulation may be there on the board.
Laptop brick might work, too, for testing at least.
But do find out if there are any issues there first, if the windings are okay, should not be too big a problem.
This should be less than $50...
Put a 24V SMPS, and another 12V SMPS or a 317 / 7812 based drop circuit to get 12V from the 24V unit, feed those to the existing secondary inputs on the PCB. That will help reduce noise from SMPS, and regulation may be there on the board.
Laptop brick might work, too, for testing at least.
But do find out if there are any issues there first, if the windings are okay, should not be too big a problem.
This should be less than $50...
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It figures, that spwindustrial place is in "bad seed" greedy insane california, where they like to think they can get away with anything.
Even is something is relatively rare, they'll inflate the price rediculously.
Bear in mind that Copper wire is about $15 a kilo now, and electrical steel has gone to $9 a kilo.
It is an odd part.
Not many people will buy it, and that may also be an issue.
You did not comment on my fix.
Please do.
It is an odd part.
Not many people will buy it, and that may also be an issue.
You did not comment on my fix.
Please do.
I will through my boxes of spare PS and semiconductors to try and make a PS as you recommended. I may have to dig around but I think I can do it !
Hello to all !
Is there any reason this transformer could not be used ?
it is dual secondary at 24V each
https://www.digikey.com/en/products/detail/hammond-manufacturing/164J48/454435
Is there any reason this transformer could not be used ?
it is dual secondary at 24V each
https://www.digikey.com/en/products/detail/hammond-manufacturing/164J48/454435
This is called 24-0-24 here.
See if similar in 12-0-12, then you get both the needed voltages, using one winding for 12V and both windings in series for 24V.
Not necessarily Hammond, same ratings, or nearly.
Size, also, not too big to fit, and termination, please check those before selection.
See if similar in 12-0-12, then you get both the needed voltages, using one winding for 12V and both windings in series for 24V.
Not necessarily Hammond, same ratings, or nearly.
Size, also, not too big to fit, and termination, please check those before selection.
