diyAudio

diyAudio (https://www.diyaudio.com/forums/index.php)
-   Analog Line Level (https://www.diyaudio.com/forums/analog-line-level/)
-   -   Potentiometer replacement preamp Esotech PII Gradiente (https://www.diyaudio.com/forums/analog-line-level/335484-potentiometer-replacement-preamp-esotech-pii-gradiente.html)

fabianoliver 19th March 2019 01:21 PM

Potentiometer replacement preamp Esotech PII Gradiente
 
3 Attachment(s)
Hello all.
i was offered with a Gradiente PII Esotech preamp, not too mutch to read about online, but it was a part of a top of the line gradiente products, alone with his amp.

It has the central pin of the potentiometer volume broken, so i need to replace it.

I've read good thinks on Alps blue velvet, but my question comes here:
( i'm a kind of handy neophite)

I see just 6 pins on all 100K potentiometer, and the original seems to have more pins, i see 7 or 8 solder points on the board.....can someone enlight me about that?
can be the 7th point i see on the board not part of the potentiometer?
Or i'm looking for a wrong part?

Any suggestion is welcome.

Fabian

craigtone 19th March 2019 01:26 PM

1 Attachment(s)
The extra connection is a loudness tap. See the attached schematic of your preamp.

fabianoliver 19th March 2019 01:48 PM

Thanks Craigtone for your repply, and schematic.
As i'm a neophite, so i can supose, that the potentiometer is a standard 8 pin like this one?

Alps RH2702 100K

ALPS 100KAX2 100K Ohm Audio Taper Stereo Potentiometer 6mm Shaft

Thanks again.

Fabian

craigtone 19th March 2019 05:46 PM

The one in your link is actually a standard stereo pot without the loudness taps. Zoom in and you'll see there are no leads on the extra 2 locations. Alps did make a version of the RH27 that had loudness taps but it will hard to distinguish real from fake on eBay if you do find one.

You can also make an external loudness tap by adding a few resistors in parallel with the pot terminals. I don't know the specifics off the top of my head but I have seen it done before.

fabianoliver 20th March 2019 12:18 PM

Thanks Craigtone.
I was thinking to pass the loudness tap. I don't mind loudness control on this preamp.
In this case, can i buy a standard alp 3 pin 100K and installing leaving unsoldered the wires that originaly went to the 4th leg?

Thanks for your enlightment!

Fabian

craigtone 20th March 2019 12:36 PM

Correct

fabianoliver 20th March 2019 01:58 PM

Thanks!!

fabianoliver 16th October 2019 03:53 AM

2 Attachment(s)
hello all again, well after some month I'm reviving this thread because today I've discovered something interesting when I dismantle it again to start to resolve the problem.

Looking at the board where the pot is mounted, I see 2 zones, a free one marked as" VR102 Volume ALPS", and the used one as: "Volume Constanta VR102".
I'm neophyte on that but they seems to use this board to mount one or the other potentiometer...

If I bought an ALPS RK27, it will fit and works ok?
What's your thoughts?

Thanks again!
Craigtone, do you jump?

sgrossklass 16th October 2019 02:41 PM

Quote:

Originally Posted by fabianoliver (https://www.diyaudio.com/forums/analog-line-level/335484-potentiometer-replacement-preamp-esotech-pii-gradiente-post5945725.html#post5945725)
I'm neophyte on that but they seems to use this board to mount one or the other potentiometer...

Looks like it indeed.
Quote:

Originally Posted by fabianoliver (https://www.diyaudio.com/forums/analog-line-level/335484-potentiometer-replacement-preamp-esotech-pii-gradiente-post5945725.html#post5945725)
If I bought an ALPS RK27, it will fit and works ok?
What's your thoughts?

1. Measure footprint to make sure it does in fact match the RK27 one, although that seems likely.
2. Make sure the RK27 matches the front panel cutouts and volume knob.
3. The original pot is labeled 100KLIN, which suggests a linear law part. Analyze the circuit to make sure they didn't use the "fake log trick". That said, it is quite possible that this would have been combined with the loudness. Back in the 1950s or so, it would have been quite common for pots to have multiple taps so you could "log law" them externally. A pot without tap would definitely have to be a log one.
4. Do you happen to know someone with a metal workshop? The old pot may still be salvageable, I'm not saying it would be easy though. If the old shaft can be removed after disassembly, making a new one on the lathe would be a relatively trivial exercise. It might even be possible to stitch the old shaft back together by drilling a hole, tapping, and inserting a screw (a rather thin and long one obviously).

fabianoliver 16th October 2019 04:10 PM

1 Attachment(s)
Hello Sgrossklas, thanks for your answer.
Here's the volume part of the diagram, can you discover something about loudness?

I see your point in trying to save the old pot, I like this kind of chalenges.
I guess I need to drill from the front the rivets, I'm right?


All times are GMT. The time now is 07:41 PM.


Search Engine Optimisation provided by DragonByte SEO (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Resources saved on this page: MySQL 17.65%
vBulletin Optimisation provided by vB Optimise (Pro) - vBulletin Mods & Addons Copyright © 2019 DragonByte Technologies Ltd.
Copyright ©1999-2019 diyAudio

Wiki