this is working before and then put in garage for almost a decade and when i tested it works relay clicked but very faint volume on both channels and some distortion, after a few days i tried it again, theres still power but no relay click, so i put it under dbt it glows then dim, i measured the DC offset which is high around 30v for all output transistors and all transistor voltages are wacky so i remove all transistor from right channel aand remove the wires that connects to tone control , input and meters, still getting the high DC offset at TP32 even theres no transistor that is installed to that particular channel, which baffles me, i tried testing the IC2 all pins are fine other than pin 4 and pin 3 which triggering the protect mode on... so i removed it and it click so the problem is on amplifier section of the board, ive been here for 3 days and couldnt figure it out, im also getting -22v in Q1 and Q2's Bases and Q20's base is also 10v which is suppose to be -.59v which is weird cos its not connected to anything i remove the wires from tone control.. ive succesfully repaired and restored my Yamaha CA-610, which is easier to work on as its pcb is service friendly and has easy access to it, badly needed your help im running out of ideas why this amp behave this way.
I'm afraid that removing the transistors and disconnecting wires to various circuit sections is the wrong way to go about this. You always fault find with it in its normal configured state, at least initially.
It all needs to be built up and in its original condition.
It all needs to be built up and in its original condition.
Follow #1 first, then:
C1 & C2 don't like that - have to be replaced / removed during repair / replaced after repair or replaced by non-pol types.
Q20 is a NPN, so +0.59 is expected, but when removed the feedback will force correction (+10V to lift the -22V at Q2).
The right channel is flipped: the minus-rail is at on the topside, the plus-rail at the bottom.
Check C11, C12, C17, C18, C21, C22, D5, D6, D7, D8, Q11, Q12, Q13, Q14.
Replace Q19 --Q22 with small-signal types (TO92) with a 1k resistor soldered to the emitter. If it breaks, there's little loss.
But more important, the feedback loop is operational again and makes error finding more logical.
That's why the protection kicks in and does not activate the output relay.so the problem is on amplifier section
On both channels! Power supply issue? Missing rail? Failing rail-caps?im also getting -22v in Q1 and Q2's Bases
C1 & C2 don't like that - have to be replaced / removed during repair / replaced after repair or replaced by non-pol types.
Notice #1.and Q20's base is also 10v which is suppose to be -.59v which is weird cos its not connected to anything
Q20 is a NPN, so +0.59 is expected, but when removed the feedback will force correction (+10V to lift the -22V at Q2).
The right channel is flipped: the minus-rail is at on the topside, the plus-rail at the bottom.
Check C11, C12, C17, C18, C21, C22, D5, D6, D7, D8, Q11, Q12, Q13, Q14.
Replace Q19 --Q22 with small-signal types (TO92) with a 1k resistor soldered to the emitter. If it breaks, there's little loss.
But more important, the feedback loop is operational again and makes error finding more logical.
I've never worked on this model but it sounds like a case of missing ground somewhere.
What was your reference point for previously stated voltage measurements?
If It has been in storage for ages look for rusted screws (ground through frame) old brown glue and corroded jumper wires, bad solders on PCB mounted ganged switches, sometimes the switch body is used as a ground jumper.
What was your reference point for previously stated voltage measurements?
If It has been in storage for ages look for rusted screws (ground through frame) old brown glue and corroded jumper wires, bad solders on PCB mounted ganged switches, sometimes the switch body is used as a ground jumper.
so i reconnected everything, aside from output transistors which tested fine ive replaced all transistors and capacitor for both channel, and now the DBT glows doesnt dimI'm afraid that removing the transistors and disconnecting wires to various circuit sections is the wrong way to go about this. You always fault find with it in its normal configured state, at least initially.
It all needs to be built up and in its original condition.
another update , i found out why the dbt is glwong, i installed npn through a pnp and and that cause short to other transistors in that channel too, i installed cheap transistor i think this is all fake from china, so i will order from mouser or digikey, i tried to remove Q15, Q17, Q19, Q21, and still getting voltage from D17 that part should be isolated because if you look at schematics removing Q15, Q17, Q19, Q21, will make D17 isolated, not connected to anything but the ground and still im getting voltage from that diode, what am i missing here?
You put PNP's where NPN's should be? And switched the amp on? Then they're dead. Check R35, R45 and D5.i installed npn through a pnp
Mark NPN's with a red dot ('red = plus rail') and the PNP's with a blue dot ('blue = minus rail').
You tried or you did remove...?i tried to remove Q15, Q17, Q19, Q21, and still getting voltage from D17
When Q15, Q17, Q19 and Q21 are removed, D17... D7 (#10!) is connected through R43 and R47 to the output (not ground), R61 is floating.will make D17 isolated, not connected to anything but the ground
See remark above; the output is not controlled by the feedback loop due to the removal of Q15, Q17, Q19 and Q21. Any value is possible now.im getting voltage from that diode
Repeated:
Replace Q19 --Q22 with small-signal types (TO92) with a 1k resistor soldered to the emitter. If it breaks, there's little loss.
But more important, the feedback loop is operational again and makes error finding more logical.
yes d7, sorry for typo's im using my phoneI can't just see a D17 in your picture. Do you mean D7?
yes Citizen124032 i did remove Q15, Q17, Q19 and Q21,
"You put PNP's where NPN's should be? And switched the amp on? Then they're dead. Check R35, R45 and D5.Mark NPN's with a red dot ('red = plus rail') and the PNP's with a blue dot ('blue = minus rail').''
The other way around, i put NPN where PNP should be, its just one transistor Q18, i did put TTC004b in there by mistake, and newly installed transistor for both channels also fail this morning its all fake i just tried them if they would work, apparently cheap transistor from china sucks, thats the only one that electronics store here from Philippines have, and the my transistors from Mouser and DIgikey ran out i have none left since ive you used most of them on my previous repairs so i tried the cheap ones, it works the first time i fired it, the next morning ,small puff of smoke and most of them tranistor ar shorted emiter to collector, ive already ordered from digikey, im just waiting for it to arrive. ive never worked in this amp before and its not that service friendly , they compacted the board, instead of laying the parts down like the resistors, its standing up to save space and its really leaves no space, and the heatsink is on top of everything, you have to remove a lot of parts to access teeny tiny bit of the board which sucks because my glasses broke. thanks for your responses , ill report back when transistors arrive
There is a conduction path through R43, the base/emitter resistor of Q19.yes d7, sorry for typo's im using my phone
Don't despair! We'll follow your pace.my glasses broke
Use the trick with the small TO92's mentioned above: they're mostly genuine and save costs.
That's why I recommend these coloured dots:i put NPN where PNP should be
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Hey Guys, the transistor arrived and i put them already and the amp is fine now its working now, all transistors voltages are correct, 3-4mvDC offset, no bias adjustment for this amp, relay click after 5 sec, everything is fine now, but the IC2 the ic for meter i think, Im getting 8v from pin 5 ,2.2k resistor connected to it tested fine, other pin have correct voltages, meter is working also, im just getting 8v from pin 5 it should be 0v..
oh yes its -8v , i guess 0v is a schematic error.I think that’s a mistake on the schematic for pin 5 voltage
how about around -8V?
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