Recapping an old pioneer amp

[patra710]

Hi I am trying to recap a pioneer sa-6700 amp that was made in the 70's.
I watch a few guys on youtube do this and they talk about different brands and series of caps in the audio and power circuits. I am a little confuse at what type to use. Any advice would be welcomed. Thanks

[kaboom]

Re: Recapping an old pioneer amp

Hi I am trying to recap a pioneer sa-6700 amp that was made in the 70's.
I watch a few guys on youtube do this and they talk about different brands and series of caps in the audio and power circuits. I am a little confuse at what type to use. Any advice would be welcomed. Thanks

Don't pay any attention to such nonsense as "the caps change the sound." Ignore it. After 35+ years, the only way new caps would change the sound is by improving it. And keeping DC leakage between stages to non-existent levels, being much nicer to power transistors and other active devices.

Panasonic FC, FM, FR, Nichicon PW, HE, PM, which even though low-esr, are just fine in hotter areas of an amp.

Only in cooler places would I use 85 degree GP caps. And only for reasons of longevity, not "sound quality." For example, stand-alone tuners, tape decks, some CD players.

Rubycons are also good, but I don't have series info at the moment.

You've probably got large snap-in or can caps in the power supply.

Replace any 2sc458 small-signal transistors- most all of them are noisy by now. Common subs are 2sc/ksc1815 or 2sc/ksc945, with 1815 preferred.

[redwire]

Re: Recapping an old pioneer amp

Electrolytics with high ESR (above 10kHz) do colour sound in a bad way.
The series kaboom mentioned are fine. The FC's are good enough. Avoid the overpriced audio-only electrolytics with silk dielectric filler and such, like the Nichicon Muse KZ, Blackgates etc.- they are about psychoacoustics and wasting cash.

[kaboom]

Re: Recapping an old pioneer amp

Electrolytics with high ESR (above 10kHz) do colour sound in a bad way.

Because they're bad and need to go.

The series kaboom mentioned are fine. The FC's are good enough. Avoid the overpriced audio-only electrolytics with silk dielectric filler and such, like the Nichicon Muse KZ, Blackgates etc.- they are about psychoacoustics and wasting cash.

Here's something I found a while ago:

http://www.roger-russell.com/truth/truth.htm
http://www.roger-russell.com/wire/wire.htm

[rhomanski]

Re: Recapping an old pioneer amp

I've done a lot of vintage 70's amps. What I use are two kinds, Nichicon PW series and Nichicon KL series. The general rule of thumb I use, if it's orange or sky blue or even tantalum, replace with KL series. Everything else use PW. PW are almost all 20% and 105degrees. KW can be found in 10% with 105 degrees. Mouser electronics has just about any size you need. The amp will sound new when your done.

Don't forget to look for the bad transistors 725's, 726's, and 1313's. You should replace the thermal grease too while you are in there.

[patra710]

Re: Recapping an old pioneer amp

Thanks for the repleys. This is my first attempt at rebuilding an old amp. I have 8 old pioneer and kenwood recievers that I want to do. This pioneer sa-6700 look like the easiest one to start. I will take your advice and hopefully do it right.

[kaboom]

Re: Recapping an old pioneer amp

Service manual attached.

Edit- If the leads on the STV3s are corroded, they can be replaced with 3 1N4004s in series.

If the STV3s should ever open, full bias will be applied to the output transistors, which will die trying to "short out" the power supply.

Something to beware of.


That Pioneer is a nice one to start with- have fun!

[rhomanski]

Re: Recapping an old pioneer amp

As Kaboom mentioned, the STV-3's deserve special handling. Usually they are held on the heat sinks by a screw with thin wires going to the circuit board. The wires are very fragile and like to break right at the body of the diode. The diode itself is very fragile and can be broken if the screw is overtightened. They are no longer made and the only way to get another is from a donor unit.

If you wish to study up on it, AudioKarma is a good website for rebuilding these. Joining is free and you can search the Pioneer forum for tips and tricks. The old units are a lot alike, although each brand has it's own problem areas. You can read about other types of units and still learn a lot about yours.

For the big power capacitors, I usually use Panasonic THA's. I end up going up in voltage to get the same physical size. If it comes with a 63V, I'll put in an 80V and it usually comes out right. You can get them from Digikey.

[Logistics]

Re: Recapping an old pioneer amp

If the main power caps are snap-in then I would replace with Panasonic TS-ED's.

[kc8adu]

Re: Recapping an old pioneer amp

seems i have seen a few with sonybond rot the leads off.
POOF!if you do the 3 1n400x be sure all 3 are in contact with the heatsink!that way the bias tracks temp.a bit of thermal compound for good measure.

Service manual attached.

Edit- If the leads on the STV3s are corroded, they can be replaced with 3 1N4004s in series.

If the STV3s should ever open, full bias will be applied to the output transistors, which will die trying to "short out" the power supply.

Something to beware of.


That Pioneer is a nice one to start with- have fun!