Chevin Research A-series schematic

[mb1]

chevin oscillator

Hello ,
you have schematic or a picture showing the parts for the chevin oscillator module (the circuit contained in the aluminum casing) mine is burnt so i cant distinquish which and where zener diodes are placed

thanks in advance

 

[gpapag]

Schematic for A6000
http://www.schematicsunlimited.com/c/chevin/chevin-a6000-amplifier-service-manual

Chevin amplifiers User Manual
http://www.ctxd.com/items/chevin.pdf

George

 

[Forman313]

I just checked most of the components on my A2000, and they seem to be ok, so im going to give it a try.

The ting is, the PCB with softstart and rectifier does not look good so im going to remove it and use a softstart module and a rectifier bridge. But im not familiar with this kind of PSU.
Does it really require that one of the mains AC wires are connected to 0v ?

 

[Forman313]

Hello ,
you have schematic or a picture showing the parts for the chevin oscillator module (the circuit contained in the aluminum casing) mine is burnt so i cant distinquish which and where zener diodes are placed

thanks in advance

I realize these pics arent much help.. nice paint job... 😡 ut I can try some measurements if possible. I have a feeling the voltage is somewhere around 350v ? I have never messed around with SMPS before, so I know very little about them..

Is it possible to measure a zener without high voltage running trough it?



-----------------------------------

Thanks alot Chevin .. its a 20 year old unit. What does it matter if you release the schematic or even better, a service manual.

 

[davidcab]

Mosefet = ECF10N25 see Profusion

 

[claudiomas]

hello, chevin A1500, +-120VDC supply, both psu module explosed i repair one but the second blow again
order nw 12X IRF840, 150p and 0.1nF film cap 4X 15V and 36V zener i hop will start nicely

 

[claudiomas]

sorry was 0.1uF i means 100nF // 1Mohm res polarized by UF4004//220kohm , zener 36V to +B 315V
this go to 6X IRF740 positiv gate rail by diac
negative rail winding gat drain for 5 IRF740 and one winding gate source for 1 IRF740
i really think should find other way, like new driver board with IR2153 or like
were to find this???

 

[Netlist]

Héhé, when they blow, they blow spectacularly. 🙂
I would think that if you fixed one side you should be able to repair the other side by carefully comparing parts.
Can't help with a schematic though.
Good luck, mighty amps.

Hugo

 

[claudiomas]

i will try to repair the chevin psu module, but i really do not like it
120V +- its too high psu blow for nothing , no rgulation no feedback crazy
i search how to built this psu with IC , shoul be very simple , 555/IR2153/3842etc or sg3525 china board....
but i need some help! any idea??? should be resonant half bridge configuration
10N/P25 are unobtainable so if lower frequency pulse widht for +-100V
means possibility of 10N/P20 easy to find

 

[claudiomas]

was few days night mare, first repair of psu module work half hour, then switched off blow a next power on.
repair again, work few minutes and blow again.*
next i use 12 IRF840 to improve original IRF740, not even start, nothing happen
back 12 new IRF740 blow immediately. so i think small pulse transformer self oscillating circuit problem.
all right, let my find a valable solution, 250V , +-125 volts i do not like at all, and 250V exicon unobtainables.
i do not need much power, so i take out everything of original power supply, capacitors fuse, transformers etc etc
and buy four meanwell 48V 150W, trimmed to max give 55V
sound fantastic and no more fear at every start on, just replace few resistors for +-15Vpsu and exicon bias polarization,
actually 25mA each transistors, four pair channel, upper board useless for home music
only 200W but beautyfull music
i compare with original full working Chevin A1500, really my mini chevin sound even better.
i will keep the A1500 for reference and in memory of good time wen i repair many Q6 for professionals
i have also one A3000 , original and full working, never had any problem,
i put this A3000 on ebay no need much power and two Chevin its enough

 

[claudiomas]

last post error, i write "i compare with original full working Chevin A1500"
error comparaison was with one original A2000 , the A1500 its the modified one.
so the amp its working perfectly so its time to find better working point,
i means higher bias, 25mA its very conservative for each transistor, just come warm
any advise?

 

[françois/ EAR]

Hi, everybody
I would like to replace the "gain" attenuators on a A-1000, because I use it with compression drivers and I have to lower the level to -18dB... I would replace by a stepped one... Maby not, but I think the sound could be better... I would like to search before having to disassemble.
Regards

 

[claudiomas]

if not mechanically brocken live it like is it
just wash with contact cleaner troughly

 

[françois/ EAR]

Thank's, Claudiomas. What contactcleaner can you recommend?
I also have a Q6 on which the potentiometers spit and manage to cut the sound depending on their position. Will it be enough to clean them, or is it better to change them? And in this case, which model to choose (value, brand)? Thank you so much.
Regards

 

[claudiomas]

hello Francois , to find original pots will be difficult, so i act like this from many years :
first day clean with standard contact cleaner F2 or C60 even WD40 specialist CONTACT CLEANER can do the job,
with small blade help open little bit, let go the spray inside many time, and rotate many time
do this two tree times all along the day, and forget , lubrification and cleaning its the purpose of thath
next day rotate well and do the same operation just one time with KONTACT CHEMIE TUNER 600, thath will work and last
this spray do not lubricate, so small splash enough
you find the magic tuner 600 from reichelt elektronics, farnell etc

 

[françois/ EAR]

Ok, I'll do like that, many thanks, Claudio.