Hi
Got the amp for £23 as spares or repair. Fancied a go as I had a spare SVI2004A chip which I did not need from China. Seller said it was working until it started going into protection from time to time but now full time.
Burned a cap C523 as soon as I plugged it in > replaced it > OK
Checked the pre drive transistors OK
Checked votages on SVI2004A Pin 1 and 16 at around 50v. Others not in spec either so I presume both channels affected.
Checked for cold solder joints > nothing yet
Replaced SVI2004A > no change (wanted to have a go at this - original probably ok and looks as if it is a genuine svi2004a)
Input selector does not work properly as it does not show red led selection. Only the yellow tape source selection.
Track on circuit board had been previously repaired. Cheked it
Any ideas / help would be appreciated ?
Thanks
Got the amp for £23 as spares or repair. Fancied a go as I had a spare SVI2004A chip which I did not need from China. Seller said it was working until it started going into protection from time to time but now full time.
Burned a cap C523 as soon as I plugged it in > replaced it > OK
Checked the pre drive transistors OK
Checked votages on SVI2004A Pin 1 and 16 at around 50v. Others not in spec either so I presume both channels affected.
Checked for cold solder joints > nothing yet
Replaced SVI2004A > no change (wanted to have a go at this - original probably ok and looks as if it is a genuine svi2004a)
Input selector does not work properly as it does not show red led selection. Only the yellow tape source selection.
Track on circuit board had been previously repaired. Cheked it
Any ideas / help would be appreciated ?
Thanks
Replace q501/q502 ! They are bad most ot the time when you measure pin 1 and 16 that voltage . Those transistor are 2sa1123 . You can use 2sa1145 or something else with Vce 100V or more.
Hi All.
With some help I have got it out of protection by replacing C523 and R535 which had also blown. Put back original SVI2004A as well as I managed to short the replacement SVI2004A which turned out to be a SVI2004C anyway. Seller gave me a partial refund on ebay as they did not know it was not an A version either and I had blown it up at that point! Also replaced relay as it was stuck.
So next issue .....The input selector does not work properly - only the tape select works so no sound. With help I know it is a power supply issue but cannot work out what to do next.
The 50v rails are around 45v but more of a concern is the 15v rail which supplies the various tone / selector / phono pre amp boards which is running at 1.89 volts.
All the Q701 - 5 regulator transistors seem to be OK (Not checked Q705 yet). The 4 rectifier diodes are OK I think with 2 showing 45v in one direction and the other two showing the same in the opposite direction.
I feel I am on the cusp of kind of fixing it or errr maybe not as it may just go into protection mode again if I get the 15v rail back!
Any help would be appreciated.
With some help I have got it out of protection by replacing C523 and R535 which had also blown. Put back original SVI2004A as well as I managed to short the replacement SVI2004A which turned out to be a SVI2004C anyway. Seller gave me a partial refund on ebay as they did not know it was not an A version either and I had blown it up at that point! Also replaced relay as it was stuck.
So next issue .....The input selector does not work properly - only the tape select works so no sound. With help I know it is a power supply issue but cannot work out what to do next.
The 50v rails are around 45v but more of a concern is the 15v rail which supplies the various tone / selector / phono pre amp boards which is running at 1.89 volts.
All the Q701 - 5 regulator transistors seem to be OK (Not checked Q705 yet). The 4 rectifier diodes are OK I think with 2 showing 45v in one direction and the other two showing the same in the opposite direction.
I feel I am on the cusp of kind of fixing it or errr maybe not as it may just go into protection mode again if I get the 15v rail back!
Any help would be appreciated.
Try looking for broken traces. shine a very bright light through the board. I had a technics with a problem like this and it was a broken trace.
q501/2 replacement
HI - dont mean to hijack this thread, but quick question -- i have a suv2x i am working with protect issues -- do you think KSA1220AYS which i have to hand is a suitable replacement ?
HI - dont mean to hijack this thread, but quick question -- i have a suv2x i am working with protect issues -- do you think KSA1220AYS which i have to hand is a suitable replacement ?
Hi grabread. I am looking through the traces. It may not be an original power supply issue at all but one of the boards. If I unplug all the boards and check the power on the J connector on the main circuit board the - voltage goes up to -18 volts.
This one is going to take time!
This one is going to take time!