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
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
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
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
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.
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
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
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
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
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
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
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
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
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?
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?
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
my posted ftp download expires (deleted) in few days i believe, so, get it before it vanishes, qinpu_pics.pdf
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
I have your PDF file now. Would you like me to delete your account information from your post? I would highly recommend this.
-Chris
Hi hewo,
Your file needs to be broken down to the original pictures. This will take me a while, like a day I think.
-Chris
Your file needs to be broken down to the original pictures. This will take me a while, like a day I think.
-Chris
Hi hewo,
Okay, your giant PDF file has been broken down into smaller chunks. Here are the four that show your amplifier off the best. I tried to give each picture a descriptive name, rather than 1,2,3,4 (actually they were 3,5,14,15 if you look).
Hopefully this will help someone recognize this amplifier if it was available under a different brand name.
-Chris
Okay, your giant PDF file has been broken down into smaller chunks. Here are the four that show your amplifier off the best. I tried to give each picture a descriptive name, rather than 1,2,3,4 (actually they were 3,5,14,15 if you look).
Hopefully this will help someone recognize this amplifier if it was available under a different brand name.
-Chris
Attachments
Hi hewo,
Once you are done you may want to put the original PCB terminals back on those two flying boards. I'm not sure if the extra wire will make the amps unstable or not.
-Chris
Once you are done you may want to put the original PCB terminals back on those two flying boards. I'm not sure if the extra wire will make the amps unstable or not.
-Chris
qinpu a3 restore
thanks for all the work folks but the real fix is to determine what prerequisite is being fouled, causing non-permission of the relay to engage, it is logic oriented, in the circuit design permissions to startup.
what prereq's would be chk'k prior to allowing relay permission?
thanks for all the work folks but the real fix is to determine what prerequisite is being fouled, causing non-permission of the relay to engage, it is logic oriented, in the circuit design permissions to startup.
what prereq's would be chk'k prior to allowing relay permission?
I would be thinking protection and AC voltage detect (power good signal). Look for DC voltage past the coupling caps on the outputs for speakers, but before the relays.
-Chris
-Chris
Hi hewo,
http://www.ti.com/lit/ds/symlink/lm1875.pdf
There is the data sheet for the chip you are using.
-Chris
http://www.ti.com/lit/ds/symlink/lm1875.pdf
There is the data sheet for the chip you are using.
-Chris
qinpu a3 poweramp ic LM1875
thank you thank you chris, been desoldering arris cablemodel sbg6580 ethernet foursome header 42 joints, rebending gold leaf fingers of three receptacles, rebending plastic distorted stretched RJ45 female socket receptacle, then restoring, then test each receptacle on timewarnercable, success 65Mbps down 10Mbps up consistent, all receptacles, but darn arris exterior plastic housing runs pretty thermal, not burn hand, but much hotter than utility company rental of twelve monthly dollars model arris cm820a/twc
okay i gotta chk powering energy into powering pin of IC LM1875, also chk if any dc spkr output on IC pin exists, gotta chl signal into LM1875 void of any dc, and should chk earthing of LM1875 should have right?
if these attributes test okay, and still relay wont fire permission granted proceed to spkrs continuity, then this creature is big headache to untangle without logistics schematic and narration of circuitry accomplishments.
thank you thank you chris, been desoldering arris cablemodel sbg6580 ethernet foursome header 42 joints, rebending gold leaf fingers of three receptacles, rebending plastic distorted stretched RJ45 female socket receptacle, then restoring, then test each receptacle on timewarnercable, success 65Mbps down 10Mbps up consistent, all receptacles, but darn arris exterior plastic housing runs pretty thermal, not burn hand, but much hotter than utility company rental of twelve monthly dollars model arris cm820a/twc
okay i gotta chk powering energy into powering pin of IC LM1875, also chk if any dc spkr output on IC pin exists, gotta chl signal into LM1875 void of any dc, and should chk earthing of LM1875 should have right?
if these attributes test okay, and still relay wont fire permission granted proceed to spkrs continuity, then this creature is big headache to untangle without logistics schematic and narration of circuitry accomplishments.
Hi hewo,
Well, hold on. Just worry about one thing at a time.
Protection is normally triggered by a few common things.
1.) Power supply fault
2.) DC voltage detected on output to speakers / headphones
3.) Power on mute circuit not working (never times out)
4.) More rare, but overload detected on one or more outputs
5.) AC detect circuit no longer works (older equipment as the fault is usually a 1 uF capacitor that has gone open
These are all common things that will trip a protection circuit.
I haven't looked, by maybe the chip has a protect output signal that trips the relay circuit. These are all just general suggestions that might remind you of something you haven't looked at yet. Happy hunting!
-Chris
Well, hold on. Just worry about one thing at a time.
Protection is normally triggered by a few common things.
1.) Power supply fault
2.) DC voltage detected on output to speakers / headphones
3.) Power on mute circuit not working (never times out)
4.) More rare, but overload detected on one or more outputs
5.) AC detect circuit no longer works (older equipment as the fault is usually a 1 uF capacitor that has gone open
These are all common things that will trip a protection circuit.
I haven't looked, by maybe the chip has a protect output signal that trips the relay circuit. These are all just general suggestions that might remind you of something you haven't looked at yet. Happy hunting!
-Chris
Five PreChks Questions
1) PS rails chk okay live
2) gotta chk dc spkrs
3) gotta chk mute hanging
4) gotta chk spkr out ovld
5) gotta chk tranny secondary sentinel watch ac presence
1) PS rails chk okay live
2) gotta chk dc spkrs
3) gotta chk mute hanging
4) gotta chk spkr out ovld
5) gotta chk tranny secondary sentinel watch ac presence
- Status
- Not open for further replies.