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Re: Small questions that don't fit anywhere
Posted: Sat May 11, 2024 4:31 pm
by Nate Dort
twelvepoint wrote: Sat May 11, 2024 8:56 am
Vintage electrical connector question:
I have a Wurlitzer electric piano and I’m working on the amplifier board. It’s about a 3x5” pcb that amplifies the pickup, drives the onboard speakers and has the tremolo circuit. Connections are made to the board with socketed wires that press onto pins on the board. The pins are circular, 1.5mm diameter and 5ish mm tall. A couple of them pulled out of the board when I was removing the wires.
So I’d like to get replacements and solder them back in, but I think these things are obsolete. Is there a modern solution to this? I can’t really use standard header blocks as the pins don’t conform to any traditional spacing. I could solder on short leads on the board and use m/f connectors but also I’m not sure what a good practice would be.
This is a bit hard to describe without a photo, but I’ll try and post one later.
I'm familiar with these. I rebuilt a couple 200-series boards and made my own tube preamp for my personal 200A.
I'd get a strip of standard header pins and cut off single pins from the strip. I think they should be large enough diameter to mate with the female barrels on the wires.
Re: Small questions that don't fit anywhere
Posted: Sat May 11, 2024 9:49 pm
by twelvepoint
I do have a bunch of those pins and thought of using them, but they seemed too thin. But I’ll take a look.
Thanks for the nice reply and I’ll let you know how it works. This wurli is the 206a, the “piano lab” model with a selector switch in lieu of vibrato. So I’m making the changes to add the vibrato as well as a line out.
Re: Small questions that don't fit anywhere
Posted: Sun May 12, 2024 11:17 am
by twelvepoint
Update on this absolutely riveting topic: these Molex connectors seem to be the right size, so I’m going to try these, and cut the male side into a pin that mounts on the pcb. That way I don’t need to swap out everything, or deal with some mix of connector types.
https://a.co/d/bGk1UAU
Sorry for this incredibly dull question.
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 12:36 pm
by benadrian
Amp nerd question.
Has anyone ever added negative feedback to an AC30 style amp? I always prefer amps with NFB. I have a boutique AC30 clone that I rarely use. I don't want to do any significant mods, but maybe adding a resistor or two in a non-destructive way might just push it into enough of a spot that I'd dig it a slight bit more.
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 1:03 pm
by jirbling rake
If you bought a used guitar or bass, and it showed up with an undisclosed small fender-type finish crack in the neck pocket, what would you do? Send it back, shake the seller down, leave it?
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 1:15 pm
by benadrian
jirbling rake wrote: Mon May 13, 2024 1:03 pm
If you bought a used guitar or bass, and it showed up with an undisclosed small fender-type finish crack in the neck pocket, what would you do? Send it back, shake the seller down, leave it?
If I bought the guitar to take out into the world and play, and the guitar was structurally sound, I'd do nothing.
If I bought the guitar to just kind of hold onto, play only at home, and expected it to increase in value and be sold later, I might contact the seller and open a discussion. I've never bought a guitar for that reason, though.
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 1:21 pm
by Dr Tony Balls
benadrian wrote: Mon May 13, 2024 12:36 pm
Has anyone ever added negative feedback to an AC30 style amp?
Leo Fender. And then later Jim Marshall but LF paved the way. Seriously, though, look at the top-boost channel of an AC30 and you'll notice its basically the same topography as a 5F6A. Gain stage -> volume control -> cathode follower -> tone stack -> LTPI. The big difference is that the normal and bright on a 5F6A blend before the cathode follower, and on an AC30 they blend before the grid of the LTPI, but that's neither here nor there.
The only think that might change is the injection point, because the VIB channel of an AC30 is connected to the other grid of the LTPI. So I think negative feedback on one grid would result in positive feedback on the other? Not sure on that though.
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 1:38 pm
by benadrian
Dr Tony Balls wrote: Mon May 13, 2024 1:21 pm
Leo Fender. And then later Jim Marshall but LF paved the way. Seriously, though, look at the top-boost channel of an AC30 and you'll notice its basically the same topography as a 5F6A. Gain stage -> volume control -> cathode follower -> tone stack -> LTPI. The big difference is that the normal and bright on a 5F6A blend before the cathode follower, and on an AC30 they blend before the grid of the LTPI, but that's neither here nor there.
The only think that might change is the injection point, because the VIB channel of an AC30 is connected to the other grid of the LTPI. So I think negative feedback on one grid would result in positive feedback on the other? Not sure on that though.
Luckily, this amp is just the Top Boost Channel. No normal channel. Should be pretty easy.
More than anything, I'm wondering if anyone has a colloquial story of "I did this mod and it worked pretty well", or "I did this mod and is SUUUUUUUUUCKED!"
Re: Small questions that don't fit anywhere
Posted: Mon May 13, 2024 2:11 pm
by Dr Tony Balls
benadrian wrote: Mon May 13, 2024 1:38 pm
Dr Tony Balls wrote: Mon May 13, 2024 1:21 pm
Leo Fender. And then later Jim Marshall but LF paved the way. Seriously, though, look at the top-boost channel of an AC30 and you'll notice its basically the same topography as a 5F6A. Gain stage -> volume control -> cathode follower -> tone stack -> LTPI. The big difference is that the normal and bright on a 5F6A blend before the cathode follower, and on an AC30 they blend before the grid of the LTPI, but that's neither here nor there.
The only think that might change is the injection point, because the VIB channel of an AC30 is connected to the other grid of the LTPI. So I think negative feedback on one grid would result in positive feedback on the other? Not sure on that though.
Luckily, this amp is just the Top Boost Channel. No normal channel. Should be pretty easy.
More than anything, I'm wondering if anyone has a colloquial story of "I did this mod and it worked pretty well", or "I did this mod and is SUUUUUUUUUCKED!"
I havent specifically done this but it should be REALLY easy to try and experiment. Like alligator clips and some components easy.
Re: Small questions that don't fit anywhere
Posted: Tue May 14, 2024 1:37 am
by jirbling rake
benadrian wrote: Mon May 13, 2024 1:15 pm
jirbling rake wrote: Mon May 13, 2024 1:03 pm
If you bought a used guitar or bass, and it showed up with an undisclosed small fender-type finish crack in the neck pocket, what would you do? Send it back, shake the seller down, leave it?
If I bought the guitar to take out into the world and play, and the guitar was structurally sound, I'd do nothing.
If I bought the guitar to just kind of hold onto, play only at home, and expected it to increase in value and be sold later, I might contact the seller and open a discussion. I've never bought a guitar for that reason, though.
Well put, and same. Usually I won't worry about a small thing like this, but was caught wondering if this was the sort of thing I should, in fact, care about.
Plays great, no problems. Thanks Ben. Good luck with the AC30-ish amp.
