hartke LH1000 Left channel slow to come on at switch on right ok

[g1]

Sorry, I wasn't clear which caps from post #8.
Any readings from post #13 ?

[Arbutt]

Hi sorry for the delay. Not been around much. I have retired . I ordered the ta7317 chip before I went away. So when I would get back to it I had the new chip.
The hartke one is an circuit board type.
Fitted the new ta7317 IC chip type. It's still the same

At switch on The faulty channel has (range 200mv)
-08.2v at the coil (r334) this not change when the relay clicks in
Checking between ground and emitters
-09.2v
I have checked the voltages compared to the working amp and they are the same on emitter and the coil.
Now I think his may of answered your questions.
I'm not as experienced and trained as you guys so please bare with me . Things I do for fun !

[nevetslab]

So, you have -9.2VDC on the output of the amp and the relay is passing that? And, you have the same on the other channel? I think we missed a step, or didn't see this DC Offset value. It looks like there is a DC offset adjust pot on the front end of the amp, as Enzo mentioned it in post # 4. See if you can trim that to 0VDC. Though I'm not so sure you can dial in THAT much of an offset with the control. The outputs on both channels need to be at 0VDC, maybe +/- 50mV or less.

[Arbutt]

Hello nevetslab when I switch on both channels have 0v on the output Jack's I have also checked before the relay kicks in the voltage on output. 0v ( pre relay). Measuring from ground to emitter both channels have the same . Scoping the output of both channels I can see nothing wrong .
I have followed Enzo's biasing and changed the 4 caps with a new ta chip.
As you stated about emitter resistors. I have 0v on the coil r334. Which is the same as the other channel .

Testing voltage on pin 8 of ta7317 I have at cold switch on I have 0.2v the relay switches on at 1.35v.
I can see on the map that there has been a different revision. Where r343 was changed from 62k to 82k..
By adjusting svr301 I can tweak it so I get 0v on output
Many thanks for the help. guys
Very patient with an old chap .
A

[nevetslab]

That's a relief, and glad the offset trim lets you dial the output to 0VDC as it should be. So, what is the outcome on the turn-on delay. Do you still have 4 times the delay on the left channel for the relay to close?

[Arbutt]

Yes I still have the delay on left channel . I forgot to measure pin 8 on the right channel. As pin 8 on left at switch on is at 0.2v rising slowly to 1.34v when the relay kicks in. Finished for the day now. Will check tomorrow.
Thanks again for your assistance on this
A

[Arbutt]

I have tested the good channel at switch on and pin 8 of the ta7317 comes on from 0v and switches on at 1v

Pin 8 on the faulty channel it starts at 0v and rises slowly at 1.3v it switches on.
I changed c316 again and tried a 62k in r343. Still no change.
I checked r342 18k on good channel . I have -68v on both sides of it. But on the faulty channel I have 0.7v on the chip side of r342 .
Checked the resistor. it ok. Changed it anyway.
I have changed ta7317 ic type about a week ago . Hartke original is a PCB type..
Thanks A

[nevetslab]

I wonder if there's a problem with the thermistor on the 'faulty' channel. That's TH301, who's circuit controls two of the transistors in the TA7317P circuit on Pin 3. Compare Pin 3 on your two amp channels. See if those are different. TH301 would be mounted somewhere in contact to the heat sink.

[Arbutt]

Thanks I will check tomorrow. I feel we are getting somewhere hopefully.

[Arbutt]

On checking the thermistor th301 and th302 on both channels the same.. voltage check from both channels is showing all 9 pins on ta7317 are the same. I have refitted the original PCB style ta7317. Still at pin 8 the voltage rises slowly and switches on at 1.1v the good channel the same but rises quicker.

The Toshiba ta7317pg should this be I direct replacement.. I have been in contact with hartke supplies in UK. But they have taken over from Korg who were the hartke dealers . New company a bit slack on getting back
Just want this sorted. Now

[nevetslab]

ANYONE ELSE HAVE A THOUGHT ON WHAT IS CAUSING ABNORMAL CURRENT FLOW OUT OF TA7317?

That +0.7V on Pin 5 bothers me, since on the good channel, it's the same -68VDC on both sides of R342. That's telling us there's almost 4mA flowing thru pin 5 of the TA7317's Q19, which gets it's current from Pin 8. So far, my brain is having trouble seeing how this is happening. But, in the good channel, there's NO current flowing thru R342, so no current being drawn thru Q19 and thru Pin 8, so that RC network of R343 and C316 are charging up normally.

You've already replaced caps C315 thru C318. C314 is set up to provide a negative voltage by half-wave rectifying the 53VAC coming in on connector CN501-a pin 6, which is used for a FAST OFF shut-down of the relay when power is turned off (TA7317 Pin 1 goes positive, turning off it's Q6 and turning off the relay driver within the chip.

I doubt if C314 is at fault, but you could try replacing it (1uF/100V). A work-around, living with this abnormal current flow out pin 5 of the chip, would be to reduce the cap value of C316 until you get close to the same turn-on time. I'd rather find WHAT is causing the current flow thru R342.

ANYONE ELSE HAVE A THOUGHT ON THIS??

[Arbutt]

I forgot to mention today when I tested the voltages on the ta chip. I had the same voltages compared to good side. I have reverted back to the original ta chip. Not sure why yesterday the 0.7v was the reading. Maybe changing the chip back. Who knows .
So just to confirm
All pins of ta7317 on faulty channel
Read the same as good channel. Except for pin 8 which just rises slowly until 1.1v ish and switch on. (8-9 secs)
Good channel switches on at 1v but rises to it in 2 secs

[nevetslab]

OK.....good information. That means no more mysterious current being siphoned out Pin 5 to draw from the charging current flowing into Pin 8, charging up C316. YET, it's still not switching on the relay at the same time. I'd hate to suggest swapping IC's between the two channels, as the same results would probably occur, and further stress the adhesive bond of the PCB solder pads. We won't go there.

If you have a resistor decade box, or even a 100k linear pot, wire it as a variable resistor, we could try putting it in parallel with R343, and dial it down in value until you find the turn-on time is the same as the other channel, then tack-solder a resistor equal or close to that pot value that speeds up the turn-on time. Kind of cheating, and leaving us to wonder WHY the two circuits are NOT working the same. That's no doubt easier than swapping out the 470uF cap for a value far lower, to speed up the switch-on time. I see in the schematic that value had been increased from 100uF to 470uF, and R343 had been increased to 82k from 62k.

That difference in RC time constant is quite large...38.5 sec for the 82k/470uF, and 6.2 sec for 62k/100uF. Any chance the parts in your other channel are 62k and 100uF?

[Arbutt]

I have some good news at last. The circuit diagram states that r343 is 82k and 470uf for c316. Rev 3.6
Reverting back to previous version 62k and 100uf . Has sorted the issue..
Would it be ok to leave like this .?
I am yet to test it.
Mr A

[nevetslab]

I have some good news at last. The circuit diagram states that r343 is 82k and 470uf for c316. Rev 3.6
Reverting back to previous version 62k and 100uf . Has sorted the issue..
Would it be ok to leave like this .?
I am yet to test it.
Mr A

"Has sorted the issue.." Are you saying the Right Ch (the good channel) has the 62k & 100uF parts for R42/C316? If so, I'd leave them, and change the Left Ch which has the extended turn-on delay to those values. Then, see if that has same/near-same turn-on delay.