hartke LH1000

[Phostenix]

That looks right to me. The emitters are the speaker out, so they should have 0 volts with no audio. The bases of the transistors should be about .5v above the emitters, and they are. The collectors are attached to the + and - voltage rails, so those numbers look right, too.

[pontiacpete]

thanks Phostenix,

Q309 and Q310 are doing the same.
Are there any other voltages checks that I could try that might lead to the source of the problem, no sound?

pete

[Enzo]

Well, if you have voltages in the powr amp and no sound, the first question is: does the speaker relay click on a second or two after power is turned on?

With test signal applied, is there strong signal on the output buss? Look for it on the legs of any of the row on 0.22 ohm 5 watt resistors or on the 10 ohm 5 w resistor parallel to the output inductor, or just look at the emitter of one of hte power transistors.. If you have it there, the amp is functioning behind the relay. There does not seem to be a DC problem on the output bus by your readings.

If the relay does not pull in, then we probably have problem with the TA7317 circuit.

[pontiacpete]

"Well, if you have voltages in the powr amp and no sound, the first question is: does the speaker relay click on a second or two after power is turned on?"

not that I am able to hear. Only the sound of fans coming on.

Went on to inject a signal and the scope on the emitter of one of big power transistors and sure enough there is signal.

Does this mean it's either the relay or the SMT/D little digital/mini component board, TA7317?

[Phostenix]

It sounds like the power amp is working, then. Do you have signal on both sides of R334?

Can you get to the relay contacts to check there?

It looks like the ouput signal goes to connector CN501-A after going through the relay. They were kind enough to put the output right next to the +72V rail on that connector, so be careful poking around the connector, but can you get a scope probe into the connector on pin 3 to see if it's there?

[pontiacpete]

I'm having a heck a time locating R334.
I can clearly see R335, but...

I'll try to probe the connector.
thanks

[pontiacpete]

oh. I found R334, it's surrounded by the inductor coil, duh.

There is a signal on the end I can reach.

Now CN501-A ..

[pontiacpete]

no signal on the out of CN501-A .

does this mean the relay is in trouble?

[Phostenix]

If you have signal on both sides of R334, I would suspect the relay, but with only 1 side, we haven't ruled R334 out. Can you see the coil clearly? Make sure it's not physically broken or burned. Wiggle it a little & make sure it's not loose - broken solder joints.

One side of R336 is tied to the relay, so if you've got audio on both sides of R336, we can rule out R334 & that coil.

Can you get to the relay? Is it socketed so that you can pull it out, by chance?

[pontiacpete]

Got a signal on the other side of R334, managed to sneak a clip lead under the coil/resistor. It's a smaller wave with a little notch on the down slop of the the upper peak before 0, but a wave non the less.

the relay is soldered in, not socketed unfortunately.

[Enzo]

If the relay is not energizing in the first place, there is little use in testing its contacts. Follow the schematic. There is voltage on the top of the coil or not, and the coil has continuity or not. D310 is across the coil, so use it as a handy test point for the relay coil.

You have signal on your output bus, good. Is there any DC offset there? Talking about multiple volts, not a few millivolts. The 7317 will detect DC and leave the relay off.

Download a data sheet on the 7317 to help you understand its function.

Samson has used the 7317 in their amps for a long time. In those when I have problems with it, it usually boils down to the small value electrolytics associated with it. Like C317, 318 in this amp.

[pontiacpete]

D310 has -73v on both side of it to ground.

oh, 7317, these caps on the mini board, I presume, do you change them off that board or do you replace the whole board?
Strike that above, found them.

Is there a way I can test these C318, 317? They are buried.

[Enzo]

I have never laid eyes on this amp, so I have zero idea how it is laid out. I check the little caps in the amps by watching their pins with a scope and seeing if they do what a cap would do to any signal there.

Meanwhile...

You have -73v on both ends of D310? We are talking about the diode next to the relay? NEGATIVE 73v?

Actually that is a good clue if it is accurate. If the voltage is really positive, then it is normal for a relay not being turned on by the 7317 chip. However, if it is trylu -73v, then I would look at R346, 3.6k 2w. Upper right on drawing, between relay coil and C350. Is it open or broken free? Is there -73v on one end and +73v on the other?

[pontiacpete]

I will try to find a point from which to check the signal through those caps.

Sorry , my mistake, it has positive 74.7v on both ends of D310(I bet it would help if I gave you the right info)

I looked up the pdf of TA7317P and it says:

"over current detecting circuit, operation at the time of over load, such as a speaker terminal short"

so if one puts an instrument cable, which has, perhaps higher capacitance(?) than a speaker cable, would this IC protect or not protect against that ?

The TA7317 is just a 9 pin op amp it doesn't look like it comes with the mini board that's attached to it.
here's pic of it:

If TA7317 were the problem, do you think this is something I would have to get from hartke,( if I were to fix it)? TA7317 itself only costs about $3.00.

[Enzo]

I think I bought my last 7317s from MCM. You should be able to get them from Samson/Hartke, or from a variety of other suppliers. I have only seen the trhough hole version in equipment. It appears they have now gone to surface mount, so watch the package wherever you order from.

Those caps are not necessarily passing signal, they may be thre to smooth out a signal. I don;t have the circuit in front of me, but sometimes they rectify a signal and filter it to ge an average level.