Hi,
I'm helping a friend with his broken IA100, he told me that it suddenly wouldn't adjust the volume.
I'v done som quick testing, one channel is running low and the other is running on max volume it seems.
I hooked up an external pre amp to main in and that worked fine.
I see that it uses a software controlled LM1972m chip for volume adjustment, can it be a software error or is the chip it self at fault. haven't found any other faulty parts yet.
I'm not that familiar with chip testing, how can i measure the chip?
PCB version: EM1070 rev.9
Also, does anybody have the service manual? Or just the schematic of the pre amp part?
edit: found schematics for IA60 looks like it uses the same PCB.
Also, R139 and R140 seems to run very hot, is that normal in this amp?
I'm helping a friend with his broken IA100, he told me that it suddenly wouldn't adjust the volume.
I'v done som quick testing, one channel is running low and the other is running on max volume it seems.
I hooked up an external pre amp to main in and that worked fine.
I see that it uses a software controlled LM1972m chip for volume adjustment, can it be a software error or is the chip it self at fault. haven't found any other faulty parts yet.
I'm not that familiar with chip testing, how can i measure the chip?
PCB version: EM1070 rev.9
Also, does anybody have the service manual? Or just the schematic of the pre amp part?
edit: found schematics for IA60 looks like it uses the same PCB.
Also, R139 and R140 seems to run very hot, is that normal in this amp?
Last edited:
Some more testing
Had limited time to test, but this is what i found. Voltage across R139 and R140 is 27,8 and 29vdc.
The voltage readings from the voltage regulators: Reg1 +7,2vdc, Reg2 -7,2vdc and reg3 +5vdc. Voltage at LM1972M vss1, vdd1 and vss2 is what the schematic says. Schematic says reg1 and 2 should have +\- 7,4vdc. Suppose 7,2vdc is close enough.
A strange thing with this amp is that it's coming audible sound from the amp itself, with no speakers connected, whats up with that?
Anyone experienced these symptoms?
Had limited time to test, but this is what i found. Voltage across R139 and R140 is 27,8 and 29vdc.
The voltage readings from the voltage regulators: Reg1 +7,2vdc, Reg2 -7,2vdc and reg3 +5vdc. Voltage at LM1972M vss1, vdd1 and vss2 is what the schematic says. Schematic says reg1 and 2 should have +\- 7,4vdc. Suppose 7,2vdc is close enough.
A strange thing with this amp is that it's coming audible sound from the amp itself, with no speakers connected, whats up with that?
Anyone experienced these symptoms?
No idea what you mean. Can you post the service manual please? I can then let you know what I think.
Hi, i don't have the service manual, just the schematics witch i found her: Thule Audio Spirit IA60 - Manual - Stereo Integrated Amplifier - HiFi Engine
It's for IA60, but they share the same PCB, EM1070.
It's for IA60, but they share the same PCB, EM1070.
Same as the manual I have then.
Possibly the electronic volume control, ... could be a number of things. Follow the audio signal from the amplifier input backwards.
Possibly the electronic volume control, ... could be a number of things. Follow the audio signal from the amplifier input backwards.
Ok, done some more testing, have consentrated on the LM1972 chip.
AC voltage at IN1 is 0,3-0,5vac goes up and down with the music.
AC voltage on OUT1 is 0,3-0,6vac goes up and down with the music.
AC voltage at IN2 is 0,3-0,5vac goes up and down with the music.
AC voltage at OUT2 is 0,01vac no mater what.
Pin 11 on LM1972, the Data IN pin has 5vdc on even numbers on the numeric volume display and 0,3vdc on odd numbers. If i understand Texas Instruments data sheet right, pin11 is for volume adjustment. Voltage at pin 11 vary when i turn the pot, 5vdc on even and 0,3 on odd numbers.
LM1972 is also getting a bit hot, no problem touching it, but still hotter than the rest of the opamps and chips.
I'm starting to suspect the LM1972m chip as the faulty part.
AC voltage at IN1 is 0,3-0,5vac goes up and down with the music.
AC voltage on OUT1 is 0,3-0,6vac goes up and down with the music.
AC voltage at IN2 is 0,3-0,5vac goes up and down with the music.
AC voltage at OUT2 is 0,01vac no mater what.
Pin 11 on LM1972, the Data IN pin has 5vdc on even numbers on the numeric volume display and 0,3vdc on odd numbers. If i understand Texas Instruments data sheet right, pin11 is for volume adjustment. Voltage at pin 11 vary when i turn the pot, 5vdc on even and 0,3 on odd numbers.
LM1972 is also getting a bit hot, no problem touching it, but still hotter than the rest of the opamps and chips.
I'm starting to suspect the LM1972m chip as the faulty part.
And there it is, working again 🙂
It was the LM1972M chip that was at fault, have ordered in a new chip from Farnell, recieved it and installed it. The amp is now working again 🙂
Now why did it get toasted in the first place? Are these chips sensitive to heat?
It was the LM1972M chip that was at fault, have ordered in a new chip from Farnell, recieved it and installed it. The amp is now working again 🙂
Now why did it get toasted in the first place? Are these chips sensitive to heat?
I'm going to revive this topic and add a little bit info from my experience. Been repairing and restoring Thule IA60 amp. Placed new original model transistors as someone did very bad things here, set bias currents, etc. Wanted to close it and after a half song it stopped working (despite it was playing good for a certain time several days ago). At last, found out low voltages +/7.4V gone and power Rs getting hot. OK, short from +7.4 to -7.4 (20 Ohm). Took off every IC which has these power supply rails coming and the last (I didn't want the most) was LM1972. It was short. Going to order a new one. I suspect one thing here - look at the power supply with those 16V caps on the 30..50V rail.. As someone wrote here in another topic, they tend to oscillate, get damaged and affect the rest ICs when exposed to such voltages. Recaped into solid state polymer of 35V - should be a little be better option.
In standby, the current is low, and voltage drop on the series resistors tapping rail voltage to the voltage regulators is low, so the input voltage to the regulators will be at the limit of what they can take. Also caps in this area had too low voltage rating. I added a separate PS for the regulators to solve this.