Accuphase E202 problem

[Chrisr3521]

Hi, just after a bit of advise on this accuphase,

The problem is when the amplifier is switched on, the relay closes for a split second then continues to work as normal as part as the protection circuit, could this be the relay on its way out? as the transistors in the circuit check ok.

Any idea's

Thanks

 

[robbie b]

protection accuphase E202

when I remember correctly there is an IC u1237 which controls the protectionsystem. After several years this IC sometimes goes bad.
When replacing this IC, also change the relay, after so many years it has burnt contacts.

Goodluck
Rob

 

[Chrisr3521]

No IC its transistor controlled.

 

[moschfet]

It is worthwhile anyway to renew all of the switches and relays in such an old amp.

 

[Chrisr3521]

The relays long out of production, and its not easy to replace.

 

[robbie b]

sorry my bad, e204 and e205 have this ic.
here is service manual, check page 18 for description of protection function
http://www.eserviceinfo.com/downloadsm/56174/Accuphase_E202.html

 

[Chrisr3521]

Yes i have it thanks, and all the circuit seems to check out, but i just want to check its just the relay thats at fault as its a major job to remove and replace it.

Just to reitarate the problem the relay fully closes as soon as the amplifier is switched on for a split second.

 

[robbie b]

Yes i have it thanks, and all the circuit seems to check out, but i just want to check its just the relay thats at fault as its a major job to remove and replace it.

Just to reitarate the problem the relay fully closes as soon as the amplifier is switched on for a split second.

my 2 cents
check the capacitors, it seems that at startup the operation voltage is causing to close the relay, afterwards due to perhaps excessive leakage or a defective capacitor, the operating voltage is never reached, thus the relay never closes again.

 

[Chrisr3521]

The relay do'es close again as stated in the first post, after the initial 'close' it then opens after a split second then operates as normal i.e after ~4 seconds Q7 turns off and Q8 turns on closing the relay.

 

[Bigred]

The relay on it's way out? Relay operation doesn't typically decline. Now the actual contacts and such are a different story. I'd say with the proper drive, the relay is either going to energize or it's not. If the relay didn't close with the proper drive then the coil resistance is a miss or open.

Are you overlooking the impedance detect part of the protection circuit? Under normal circumstances the relay WILL close right after powering on. Without the speaker terminals connected to the impedance detect circuit, how would it detect an abnormal load or not? Everything being normal, you should be able to hear the low level AC signal during the delay and DC detect period.

 

[tauro0221]

Hi,
Did you check the output voltage when you power on the amplifier? Check the output voltage when you applied power to the amplifier. It is possible that the protection circuit it is detecting high voltage at the speaker output.

 

[Chrisr3521]

Hi,
Did you check the output voltage when you power on the amplifier? Check the output voltage when you applied power to the amplifier. It is possible that the protection circuit it is detecting high voltage at the speaker output.

It's not detecting high voltage as it works as it should after the initial activation.

It seems the the initial inrushing d.c is causing the relay to momentarely activate, has anyone any other ideas?

 

[Chrisr3521]

Anyone?

Schematic below.

 

[tauro0221]

Hi,
Here it is a link for the services manual. Check page 12. It look like what it is doing is normal. In the power on the relay should energizes for 4 seconds and then drop.
Link:Accuphase E-202 | Owners Manual, Service Manual, Schematics, Free Download | HiFi Engine

 

[Chrisr3521]

Yep it does exactly what it says on page 12, I know how the protection circuit is supposed to and does work, but as I have said as soon as the power switch is pressed on, the relay connects the amplifier to the speakers for a split second then disconnects, it's not supposed to do that, after it does this it follows the normal protection circuit procedure.

 

[tauro0221]

Hi,
Okay I missed the first part. Check then the transistors Q1 thru Q8. These transistors are the one that does the delay and check for output voltage to set or reset the relay. I will check Q3 and Q4. Q8 is the one that enable the relays.

 

[Chrisr3521]

All the transistors check out.

 

[tauro0221]

I did some checked and this it is what I think it happening at the power up. Q1 and Q2 are the one that sense high voltage at speaker outputs. Lets check the voltage at the base of Q1 when the amp it is power up. Check the voltage and it should read zero. When power it is applied voltage it is applied directly from the bridge to the base of Q3. I think the delay it is done in the Q3/Q4 by C2=10/25 volts and C3=33/volts. This will delay the close of the output relay at the power up. Check bot capacitors to see if they are OKAY. Do you have a scope?

 

[Chrisr3521]

All voltages are correct apart from the base of q8 which reads 4v any idea why?

 

[tauro0221]

HI,
I think 4 volts at the base of Q8 it is OKAY. To be able to close the output relay the base of Q8 must be positive. In the schematic showed that the base voltage should be 4.4 volts. In the explanation on page 12 for the circuit in the power ON it is say that the delay of 4 seconds it is done by the charging of capacitor C8. That will hold the relay open for 4 seconds. Can you check the voltage at the collector of Q6. If it is leaking it will charge the capacitor faster. It should be zero volts.