AP35 surprise

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Raul_77
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AP35 surprise

Unread post by Raul_77 » Mon Jan 14, 2019 3:59 am

A friend bought an AP35 with a broken channel and asked me to fix it. The problem was simply the output transistors, the emitter resistors and another pair of small resistors burned, After changing all this I took advantage of to change also the electrolytic capacitors, which were already many years old, the main ones of 4,700uF are exchanged for Elna LAO of 10,000uF and the 6 of 47uF in the pcb's by Jackon LHK Low ESR, also of 47uF.

The main capacitors and pcb's are glued with strong glue, as I did not have I used this double-sided adhesive tape, which also promises a strong bond:

http://mundoceys.com/producto/36/bricocinta

And this is where the surprise comes: the sound became much warmer and more pleasant, it really makes you want to make long listens. I have changed capacitors for better ones many times and I have never found this effect, so I attribute it to the tape. The tape is 1mm thick and is made of what looks like some kind of silicone, I suppose its effect has been to dampen some kind of vibrations and that is the origin of the sound improvement.

I put it here in case someone wants to repeat it, it's easy, cheap and harmless, you can easily go back if the result does not please us.

My friend is really delighted with his AP35, what is described as 'a delight'.

Regards

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Dr Bunsen Honeydew
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Re: AP35 surprise

Unread post by Dr Bunsen Honeydew » Mon Jan 14, 2019 9:40 am

Tape makes no difference. The difference is using 10kuf.

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Fretless
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Re: AP35 surprise

Unread post by Fretless » Mon Jan 14, 2019 10:38 am

Image

Quite an old model, the NVA AP35. I remember a friend of mine in Scarborough had one back in the 80's, running a pair of Linn Kans from (if I'm right) a Rega Planar TT.
Main: NVA: P50sa - SSP - A40 - LS6 - Cube2
Pi: Allo DigiOne Signature/Volumio/Tomanek LPSU/Jitterbug
DAC: Metrum Acoustics Musette CD Transport: Cambridge CXC
Headphones: AQ NightHawk & NightOwl Amp: Schiit Magni-3
DAC: Cambridge DacMagic Plus + Sbooster LPSU

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Dr Bunsen Honeydew
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Re: AP35 surprise

Unread post by Dr Bunsen Honeydew » Mon Jan 14, 2019 11:32 am

Late 80's early 90's

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Raul_77
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Re: AP35 surprise

Unread post by Raul_77 » Tue Jan 15, 2019 2:48 am

Thanks for your response, Mr. Dunn. Then two questions, please:

1- Change the 47uF capacitors for others of 100uF, or more, is it also an improvement or is it a bad idea?

2- The pcb's have jumpers that join the three stages of the amplifier, to be able to separate them and add individual supplys for each one. Could these jumpers be soldered to an electrolytic capacitor to each one, for example of 100uF or more, between the jumper and ground to add local filtrate to each stage? Good or bad idea?

Sincerely

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Dr Bunsen Honeydew
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Re: AP35 surprise

Unread post by Dr Bunsen Honeydew » Tue Jan 15, 2019 10:01 am

I don't advice people on modifying my designs. You do what you like and you take responsibility for it.

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