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Philips AG9016 right channel sound

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New to the forum.

I get a ruffled/muffled type sound out of the RH side of the amp.
It is intermittent
I have changed over speaker cables and sound transfers to the LH side.
Any help would be appreciated.
This is my first Tube/Valve amp

Other than that it sounds sweet running my Dual 1229 through Sonab OA5s speakers

Regards

Mike
 

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I see that the inside is still all original, nice find. Try exchanging the left/right tubes first, one of them may be faulty. There may be a bad/intermittent socket connection. Tap lightly on the top of the tubes with a wooden/insulated stick to check. Clean the tube pins with a type 600 sandpaper. On this amplifier, the paper capacitors across the output transformer primary are likely to fail. They are covered in tar-like black compound, and are attached to each transformer. You may disconnect them completely.
 
Thanks

Cheers pcan

I have swapped over and cleaned the pins as instructed, will run for a few hours to see if it comes back.

I have tried different sets of EL95s, got a pair of mullards in at the moment

Do I need to replace the paper caps and if so what value are they?

Mike
 
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If the contact cleaning solves the issue, I would not do any further changes yet. Most issues on this type of vintage small amplifiers are related to contact oxidation and cleaning them is all that's needed. Paper and electrolytic capacitors should be replaced sooner or later, and the selenium rectifier is even less reliable (and dangerous, when it finally fails), but it's best to do it properly, taking the time to plan it. The AG9016 is quite popular and if you feel that your amplifier needs a repair, you will easily find the schematic and several restoration guides. Since you like this technology, I suggest to also try other tube amplifiers before committing further money on the AG9016. It has been a commercial succes for a reason, and is still going strong today, but the output transformers are very small and of lesser quality than other modern and vintage tube equipment.
 
Clip one lead of the black caps sitting on the output transformers. Your sound quality will improve significantly, and it may solve your issue. Those caps have no place in this amp.
C13 and C35 stop any HF oscillation and helps stability of the amplifier. If they had "No place" in this amplifier, I am sure Philips would not have included them.
 

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Thanks guys, I have cut one wire on each of the black caps across the output transformers, I am still getting a noise from the right hand side. I am convinced there is a drop in volume between the speakers as sometimes it jumps back into life.
I have recorded the sound online, here is the link

Philips AG9016 Noise Pictures, Philips AG9016 Noise Images, Philips AG9016 Noise Photos, Philips AG9016 Noise Videos - User Media - TinyPic - Free Image Hosting, Photo Sharing & Video Hosting

Regards
Mike
 
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Those capacitors are a standard feature of the radio/TV Philips designs of the time, therefore they are also in this mass marketed amplifier, altough they are uncommon on Hi-Fi tube amplifiers in general. I would be cautious about removing them alltogheter without further checks. They may fail and produce muffled sounds as a result. If the original issue will surface again, disconnecting them may be the next troubleshooting step. But if they work as they should, I dont feel compelled to remove them. The audible attenuation effect is tiny and may even be welcome, because they will also attenuate some of the high order distortion. At very least, the modification should be checked. This entry level amplifier was never marketed as Hi-Fi device, the attached service manual for the authorized Philips dealers does not mention high fidelity operation at all. It was mainly intended to be connected to a crystal pick-up or a radio, and neither of them had a flat 20Hz-20KHz output.
Back to the original poster question, another common cause of intermittent faults on some Philips devices of the time is a bad connection between a resistor metal contact and the carbon paste inside. It may be checked by pocking all resistors with a insulated stick.
 

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Thanks, I have reconnected the cut wire on each of the black caps across the output transformers. I noticed when powering up that one of the ECC83 tubes lit up and other did not. I have for now replaced the ECC83s with a set of brand new shiny pin Russian tubes and am running her in to observe.

Mike
 
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It doesn't look like any components have been replaced so at best the amp is running on borrowed time, at minimum all of the electrolytics should be replaced. There may be other components such as resistors and small film/paper caps (tone controls/coupling) that are failing and need to be replaced.
 
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