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Old 30th June 2015, 06:00 PM   #1
hewo is offline hewo  United States
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Default qinpu a3 doesn't relay click

Can't get relay to click, can't get factory assist, but examination reveals as follows

1. Tranny secondaries all good output
2. Replaced all zeners, tubes, poweramp ic's both, all five 9014's, single d667, and single 7806
3.one of the two 9.1 zener is not producing 9.1, dunno why, maybe it engages after relay clicks?
4. Tubes heaters alive
5. Twin blue led's blink forever, and 7806 fin gets too hot, maybe junk new 7806?
6. Poweramp chips called 1875, five legged.

Can't obtain any schematic
Pl assist restore operability
Thanks
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Old 1st July 2015, 05:04 AM   #2
anatech is offline anatech  Canada
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Hi hewo,
Can you provide any history as to what happened to the amplifier? Can you at least take a couple pictures of the circuits?

Have you looked up the datasheet for the 1875 power amp chips? They should provide a close schematic to that stage of your amplifier.

Replacing stuff without a good idea of the problem can easily create more problems that need to be fixed. You should start by getting some idea of how the circuit works, just a general idea at least. Go from there.

So, tell us what conditions would keep the amplifier in protect mode. From there you can check for those conditions.

-Chris
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Old 1st July 2015, 05:48 PM   #3
hewo is offline hewo  United States
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I'll get some cellphone pics of the mobo both sides, 1875 app shts too if avail, client said just keeps flashing doesn't amp anymore. Qinpu abandoned me once disassemble pics emailed, their request, for legitimacy proceed.
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Old 1st July 2015, 06:22 PM   #4
anatech is offline anatech  Canada
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Hi hewo,
It sounds like you are more at home with fixing computers. This is an entirely different world compared to computer service.

Look up LM1875. That will give you the information on that section.

Client. Are you repairing this as a business?

Quipu was talking to you at some point in time I guess. But the way you post is difficult for me to follow. Can you please revert to normal conversational grammar? So the pictures that Quipu requested from you, can you post them here, and what was the reason Quipu requested the pictures? I want to get a picture of the situation. This amplifier sounds like a hybrid signal tube and IC output thing. In the circuitry you probably have some high voltage circuits as well as the normal low voltage - higher current solid state levels.

Things that might help are voltage readings from the power supplies, voltages around the tube(s) as well as some voltage readings from the speaker relay contacts. This is in addition to pictures you may have.

-Chris
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Old 1st July 2015, 06:33 PM   #5
anatech is offline anatech  Canada
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Hi hewo,
A little look on Google tells me that this is a $200 (street price) headphone amplifier. The LM1875 is running with supply voltages around +/- 15 VDC, well below the maximum of +/- 30 VDC. The chip should be reliable. It uses a pair of Russian tubes as signal amplifiers. The plate voltage would be interesting to find out.

Are the heaters working? The tubes should feel warm, you might be able to see the glow from the heaters on about a 45 angle down from the top.

-Chris
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Old 1st July 2015, 08:17 PM   #6
hewo is offline hewo  United States
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Yup, I've been sucked in after success prior repairs this forum, so outsiders dump their gear onto me to repair, kinda word of mouth. This qinpu problem is likely a dead feed for permissivity conglomerate prereq's prior to firing coil relay.
I chk'k the tranny secondaries ok, downstrm dc a bit confusing without schematic.
Factory engr contact scared off? Pics were only mobo and appurtenances disassembled complete, not closeup as you will be getting.
Resistors are all 1/8w except coil feed dc 1/4w 220 ohm
Pl stndby pics, I have disease, encephalopathy, succinct writing, please bear with me
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Old 2nd July 2015, 02:49 AM   #7
anatech is offline anatech  Canada
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Hi hewo,
I'm very sorry to hear you have this problem. Would you mind if I asked which type? You do not have to answer if it makes you the least bit uncomfortable.

This may have scared your factory contact off. We'll do our best to understand your meaning in posts.

The pictures might be helpful. By chance, did you have a chance to measure the supply voltages and the DC offset voltages?

-Chris
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Old 2nd July 2015, 03:09 AM   #8
hewo is offline hewo  United States
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Default qinpu_pics

this site wont take cellphone pics, too Mb biggy, so goto ftp dwnld:

<removed information at member's request>

it's easy fix, some prereq not permissible, so conglomerate prereq's not met, so logic analog circuit refuses activate relay coil excite, right?

gotta restore china 7806 since ebay 7806 finning too hot

yup always heaters russian tube replcmnts glowing 6dc volts by regulator

remember one of two zener 9.1V does not have 9.1vdc across it, why, relay unengaged yet?, or fault lies around this sector circuitry

remember ALL zeners replaced, all 9014's replaced, D667 replaced, IC 1875's pair replaced, tubes replaced by russia tubes, 7806 replaced, cheap stuff, still no go

also notice umbillicaled 1875"s via flex ribbon (stolen from scrap ide cable), factory was rightangled rigid headers, very unfriendly, btw, mica TO-220 insulatory crappy, keeps delaminating as mineral sheet layers ultra thin, gotta utilize grey fabric weave heat silicone transfer pads, no thermal grease legacy compound.

so why was qinpu scared off?





Quote:
Originally Posted by anatech View Post
Hi hewo,
I'm very sorry to hear you have this problem. Would you mind if I asked which type? You do not have to answer if it makes you the least bit uncomfortable.

This may have scared your factory contact off. We'll do our best to understand your meaning in posts.

The pictures might be helpful. By chance, did you have a chance to measure the supply voltages and the DC offset voltages?

-Chris
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Old 2nd July 2015, 03:13 AM   #9
hewo is offline hewo  United States
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Join Date: Feb 2010
Default ftp picture downloads expiration warning

my posted ftp download expires (deleted) in few days i believe, so, get it before it vanishes, qinpu_pics.pdf




Quote:
Originally Posted by anatech View Post
Hi hewo,
I'm very sorry to hear you have this problem. Would you mind if I asked which type? You do not have to answer if it makes you the least bit uncomfortable.

This may have scared your factory contact off. We'll do our best to understand your meaning in posts.

The pictures might be helpful. By chance, did you have a chance to measure the supply voltages and the DC offset voltages?

-Chris
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Old 2nd July 2015, 03:19 AM   #10
anatech is offline anatech  Canada
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Hi hewo,
I have your PDF file now. Would you like me to delete your account information from your post? I would highly recommend this.

-Chris
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