Hello Everyone,
I have a Primare A30.1 integrated amplifier having a problem on the right power amplifier. The speaker protector do not connect the speaker to the power amplifier when it is powered up, because there is a 0.6VDC at the power amplifier output.
I have soldered a speaker to right power amplifier's output, it can have music output without hearable distortion. What component you would suspected to cause the DC offset??
Thanks for any input!
Best regards,
William
I have a Primare A30.1 integrated amplifier having a problem on the right power amplifier. The speaker protector do not connect the speaker to the power amplifier when it is powered up, because there is a 0.6VDC at the power amplifier output.
I have soldered a speaker to right power amplifier's output, it can have music output without hearable distortion. What component you would suspected to cause the DC offset??
Thanks for any input!
Best regards,
William
Hi,
William and I are working this amplifier.
Seems to me that this integated amplifier is using BTL output. Speaker is floating, not on ground. It is difficult to find out which component caused the offset. Hoping somebody can shed some light on this.
There are 2 big power transformers for L and R channel. Each transformer only has one output winding (28V ac, no center tap), feeded to the bridge rectifier.
4 big transistors are used on 1 channel, they are not connected as parallel. Instead, they are 2 separate outputs, speaker is connected at BTL.
No idea whether the 0.6V trigger the speaker protector. Or there is a problem on protector circuit.
We do not have Primare 30.1 integrated circuit diagram.
Best regards,
Norman
William and I are working this amplifier.
Seems to me that this integated amplifier is using BTL output. Speaker is floating, not on ground. It is difficult to find out which component caused the offset. Hoping somebody can shed some light on this.
There are 2 big power transformers for L and R channel. Each transformer only has one output winding (28V ac, no center tap), feeded to the bridge rectifier.
4 big transistors are used on 1 channel, they are not connected as parallel. Instead, they are 2 separate outputs, speaker is connected at BTL.
No idea whether the 0.6V trigger the speaker protector. Or there is a problem on protector circuit.
We do not have Primare 30.1 integrated circuit diagram.
Best regards,
Norman
Try to get a schematic, otherwise it's just a guessing game.
Worst case, lift it yourself with paper and pencil 🙁
Worst case, lift it yourself with paper and pencil 🙁
Yes, I agreed, it is difficult to find. Appreciate any reply. Already with pencil and camera to scratch the circuit. They used surface mount, difficult to trace.
The protection circuit used two units of surface mount Philips NAND gate HEF4093BT to drive two 24V relays. Both relays do not latch.
No idea why both relays not latched if RHS having 0.6VDC, LHS is normal (LHS relay should latched).
The protection circuit used two units of surface mount Philips NAND gate HEF4093BT to drive two 24V relays. Both relays do not latch.
No idea why both relays not latched if RHS having 0.6VDC, LHS is normal (LHS relay should latched).
Next step is to use two units of small VA transformers to replace the big one for indepth troubleshooting.
It is difficult to find the circuit diagram.
Appreciate anybody can help on giving me the circuit diagram, or a portion of it which focus on the line amp and the power amp section.
Thanks and best regards,
Norman
Appreciate anybody can help on giving me the circuit diagram, or a portion of it which focus on the line amp and the power amp section.
Thanks and best regards,
Norman
If you find a problem with a surface mount part, are you going to buy a $600 hot air soldering station to repair it?
Cheaper to salvage the power transformers and heat sinks, maybe salvage the output transistors and relays, and buy an amplifier board with components with leads on them. Or make one with perf board. diyaudio.
Cheaper to salvage the power transformers and heat sinks, maybe salvage the output transistors and relays, and buy an amplifier board with components with leads on them. Or make one with perf board. diyaudio.
I have the soldering tool. In fact, I would like to preserve the unit in original shape and design. Also, I wanted to reduce soldering out unrelated component during trouble-shooting.
Primare may not release the circuit because I am not their dealer.
Best regards,
Norman
Primare may not release the circuit because I am not their dealer.
Best regards,
Norman
There is an OPamp 1458 next to the speaker relay, anybody knows its function?
Is it an o/p DC detecting circuit that feeds the fault signal to the 'protection circuit'?
Thanks,
Norman
Is it an o/p DC detecting circuit that feeds the fault signal to the 'protection circuit'?
Thanks,
Norman
Circuit of A30.2 power amp not looks like the A30.1 integrated amp in following views:
- The output transistors of A30.1 are not collected in parallel.
- The A30.1's speaker is connected to the emitter of the transistor pair.
- The A30.1 has no transistor (Q106,Q6 on A30.2 diagram) next to the OPamp/relay.
- The output transistors of A30.1 are not collected in parallel.
- The A30.1's speaker is connected to the emitter of the transistor pair.
- The A30.1 has no transistor (Q106,Q6 on A30.2 diagram) next to the OPamp/relay.
Still trying to seek for the Primare 30.1 integrated amplifier circuit diagram. Hoping somebody can help to find it out.
The 0.6VDC at the +/- speaker terminal is not acceptable. The PNP power transistor pair conducted more the NPN. As a result, the speaker terminals unable to get 1/2 VCC reference to the main capacitor. I got 35V at the output, the correct reading should be 25V.
I would suspected the K170 (should be 2SK170 FET) differential input transistors that caused the offset. This amplifier is full balance in design across the line amp and output amp. It is difficult to do more measurement without a diagram.
Please help.
Best regards,
Norman
The 0.6VDC at the +/- speaker terminal is not acceptable. The PNP power transistor pair conducted more the NPN. As a result, the speaker terminals unable to get 1/2 VCC reference to the main capacitor. I got 35V at the output, the correct reading should be 25V.
I would suspected the K170 (should be 2SK170 FET) differential input transistors that caused the offset. This amplifier is full balance in design across the line amp and output amp. It is difficult to do more measurement without a diagram.
Please help.
Best regards,
Norman
The OP-Amp is set up as servo control for the offset.
At least it is in the A30.2 poweramp.
I have the schematics for that one if You want it.
I believe it is identical to the poweramp section in Yours.
I have confirmed the K170 is in good condition, not related to the offset.
Thanks for Tandbergeren. I have the 30.2 poweramp diagram. Seems it is not the same design as 30.1 integrated amplifier.
The 30.1's BTL output, the offset output voltage is 25Vdc (reference to +/- VCC). Whereas, the 30.2 power amp is not BTL, it should have 0V reference to ground.
Thanks,
Norman
Thanks for Tandbergeren. I have the 30.2 poweramp diagram. Seems it is not the same design as 30.1 integrated amplifier.
The 30.1's BTL output, the offset output voltage is 25Vdc (reference to +/- VCC). Whereas, the 30.2 power amp is not BTL, it should have 0V reference to ground.
Thanks,
Norman
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