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Post by paradisecs on Dec 16, 2018 4:11:38 GMT
I just rebuilt a SHP3 Code C. All lytics replaced, all transistors, all resistors even close to being out of spec, as well as the diodes on the drive and preamp boards, and new bias pots. I've done three now and the bench test on this one seems good and the bias is set. One thing I've noticed that I haven't seen on the others I've rebuilt or the ones I have waiting to rebuild is that at power on I hear and feel the relay clicking. Is this something to be concerned about or is this normal and it is just more noticeable on this particular amp?
Stephen
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Post by robnyc on Dec 16, 2018 5:10:16 GMT
NO, it is not normal. If it only happens with mech connected look for a problem in the harness wiring or mech cam switches. If it happens with no mech connected, it is the relay itself. Try another one. DC is always present in the relay coil and the circuit is completed by simply grounding the other coil terminal. If the relay has leakage it will either blow the fuse or chatter.
RobNYC
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Post by paradisecs on Dec 16, 2018 7:12:02 GMT
This is just on the bench at this point...no mech. I'll pull one from another unit and see what happens. Do you know of a new replacement for these relays? Could there be a ground short to look for?
Stephen
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Post by Ron Rich on Dec 16, 2018 13:52:12 GMT
Stephen,
If on the bench, there is no way it should pull in, when power is supplied-- check the diode across it-- and follow the schematic-- you will find that the ground return goes to several places, check them. Which relay do you have installed in the amp? Is it modified for use in a SHP ? If installed in the phono--and the phono is in scan mode, it SHOULD pull in when power is applied. Yes--NTE makes "replacements"--Ron Rich
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Post by robnyc on Dec 16, 2018 15:25:55 GMT
This is just on the bench at this point...no mech. I'll pull one from another unit and see what happens. Do you know of a new replacement for these relays? Could there be a ground short to look for? Stephen Stephen, this is going to be something simple. The switched side of the circuit goes to pin 3 on the mechanism plug and pin 10 on the volume control plug -that one is the 'reject'. Something is touching ground. Similarly, look for touching solder tabs on the relay socket. I've run into odd situations like this often when buying amps or other electronics that have been "knocking around" outside of a machine. Things get squished. Rob |
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Post by paradisecs on Dec 16, 2018 21:50:43 GMT
Relay type Guardian Electric 1315 series. I swapped one out from my working unit and same issue. I then swapped the amp in to my working STD160 and I don't get sound. I can hear the sound from the needle but no output. I also don't get that "pop" you get when turning one of the units on. Bias voltages are still good. Gain didn't change anything. And just to try it, I swapped out the preamp board from my working system and that didn't change things either. I went ahead and reflowed all the solder joints.
- side voltage of C5152 & C5137 is 368mV and 398mV respectively. Getting +25 at the 32v test point and -25 at the -32v on R51.
I have not have a short in the relay circuit as of yet. Is the voltage at C52/57 related to the relay? I could swap in a driver board to test but I'd rather not rick my new transistors.
Stephen
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Post by robnyc on Dec 17, 2018 10:39:13 GMT
Stephen;
IS the volume control plugged-in?
Are the speakers connected properly?
Is the relay staying pulled-in? If in a machine it would also trip the mech. If on a bench, just remove the relay and see if sound comes n. It will be low due to the squelch voltage not being grounded out by the relay.
Pins 11 & 5 are the inputs to the driver bd from the volume control. With record playing there should be signal at the high side of the volume control and driver input.
The protection ckt might be activated for some reason but applying signal at the volume control bypasses that. If the protect ckt is suspected try starting a record with volume all the way down and slowly bringing it up. The protect is based on emitter current sampled at the finals, so it is possible to sneak in some signal before the fault current gets high enough to trip it.
At this stage you should be running that amp through a current limiting bulb of no more than 40 w.
RobNYC
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Post by Ron Rich on Dec 17, 2018 14:16:33 GMT
Stephen,
Something in the power supply is causing a problem--25 volts at the 32 test points, just won't cut it-- are you using a dim bulb testor on that amp --as Rob stated, you sure should be !! Did you check the diode on the relay ?? Ron Rich
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Post by paradisecs on Dec 18, 2018 5:20:00 GMT
Yes, I always have the dim bulb tester. I'm only getting 26 volts out of the c65/66 replacements I installed as well as at the cr12-15 diodes (not replaced). Could this be just bad new driver caps or could there be something wrong with the transformer? How would I test it? I've got 91VAC before the transformer.
Stephen
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Post by Ron Rich on Dec 18, 2018 13:54:24 GMT
Stephen,
"91 volts", AC, I assume ? Is that lamp lit ?? I use a 95 watt "Miser" lamp--it stays nearly off and the 32 volt readings are around 31.5, when all is OK. I have never measured incoming AC voltage, but I would guess with it that low, you would only have low DC measurements. Un plug the boards, and re-measure-- Ron Rich
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Post by paradisecs on Dec 20, 2018 0:23:05 GMT
Still on the bench (no mech, input, or speakers) I took the amp off of my dim bulb tester and plugged directly to my surge strip. My voltages come in at 31.5 now. Is my bulb drawing to much power or does that indicate a problem with my dim bulb tester?
Stephen
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Post by Ron Rich on Dec 20, 2018 0:29:51 GMT
Stephen,
Somethings "Not rite--er, write--no-- not correct" ! I'll attempt to remember to check what the line voltages reads., with my dim bulb testor in line tomorrow, and let you know--remind me iffin I forgetz ! Ron Rich
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Post by robnyc on Dec 20, 2018 1:13:35 GMT
Stephen, I'm using an SHP 1 here for comp audio. Quiescent with 119 vac at the wall I see 106 through a 40 watt bulb. there is barely any filament glow.
At idle, the current draw is dependent on idle bias. I use approx 1.5 ma. These amps will produce sound down to approx 71vac and distort badly below that.
I don't think this is a power issue, but it is something common to both channels. have you done any of the tests I suggested?
RobNYC
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Post by paradisecs on Dec 20, 2018 2:18:28 GMT
I'm going through your suggestions next. I wanted to rule out an AC power or cap issue before I did anything else. At my bench I don't have a way of getting input audio or speaker output at the moment so I have to swap the amp in to my STD in the living room when I test sound. The wife's at choir tonight so the kids are going to bed early and hopefully I can work on what you suggested.
Stephen
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Post by paradisecs on Dec 22, 2018 3:01:02 GMT
Here's an update - still not working but I'm learning the circuits a little more so there is a plus. I think I've cored everything you both have suggested.
Installed amp to a working STD160
Volume control plugged in.
Speakers connected properly
Relay socket is crimped, not soldered, and I do not see a short
Tried relay from another unit - no change
Relay seems to be working (and I don't hear it click anymore at power on)...records play then reject and move to the next record. Loud hum with this amp installed vs the one that goes in the unit.
Tried with volume all the way off at start of record and no change.
DC voltages with record playing at junction of R90 & Q22/23 and junction of R67 RQ12/13 is -1.9 instead of -.7 per schematics. And others not correct either but I can't find my notes so I'll have to retest them later. I had to get the working amp back in so the Christmas records could be played.
Stephen
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