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Author Topic: Randall rg-80 rg-100 power amp transistors  (Read 2987 times)

duckduckgoose

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Randall rg-80 rg-100 power amp transistors
« on: February 16, 2020, 10:44:10 AM »
Anyone know if randall is still using 2n6264 transistors in their current amp?
I know they are still using FET for preamp but I'm curious about still using the output npn transistors or if they switched to using opamps for the output.

edit:
there is all kinds of info about the power amp in this thread if anyone is interested
https://www.ssguitar.com/index.php?topic=2324.0
« Last Edit: March 16, 2020, 08:02:29 PM by duckduckgoose »

Enzo

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #1 on: February 16, 2020, 12:21:50 PM »
Op amps?

That part number is a rather light weight TO3, and I can think of a lot of more modern parts I would put in an amp instead.

duckduckgoose

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #2 on: February 16, 2020, 04:53:48 PM »
yeah the old schematic had rca 2n6254 tis98 on the output. I guess thats TO3. I'm wondering what they use in their current rg-80 amps. They don't have a schematic for the newer ones and the pcb looks different. I want to make a clone of the original rg-100es power amp and pre amp.

duckduckgoose

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #3 on: February 16, 2020, 05:21:07 PM »
sorry if last post was confusing. I think they are also called ic chips. I don't think randall used the ic chips in the original for the output. wonder what they are using now because those rca npn's are hard to find and expensive. they are no longer made.

in these pictures you can see the npn's sheilded by metal. I wonder if they use those in their current model rg80 rg100.
here is a picture of what I guess is an older randall pcb.
https://ibb.co/f4hKG79
here are the npn transistors on top with the metal fins in between them
https://ibb.co/qCyRW3N
this looks like I guess a newer ones pcb but still not new new
https://ibb.co/6HFkMzf

does it make a difference? hmmmm

« Last Edit: February 16, 2020, 05:22:16 PM by duckduckgoose »

Enzo

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #4 on: February 17, 2020, 12:43:35 AM »
There are plenty of modern TO3 transistors you could use, it really isn't an issue.

Your PC board photo LOOKS like large power transistors are in use.

duckduckgoose

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #5 on: February 17, 2020, 06:59:03 AM »
I found this on another forum about fender keyboard tha uses 2n6254 on the output.

"The original RCAs were those old hometaxial types - which are now unobtainium. In its time, the 2N6254 was basically a "super 2N3055". The closest thing currently available and least likely to give you grief is the 2N3773. If the faster modern version causes oscillation, usually adding a base stopper resistor will fix it. In many of the older circuits that didn't have gobs of loop gain, increased output stage speed doesn't cause any problems."

really curious what randall is currently using. the last update on schematic was 1985 and just 2 years later they sold the company.

jameco has some 2N6254 npn to3 for $10 each. I might try those and see how it sounds. I gotta read up some more to make sure I don't shock myself though lol. I made a preamp but that's lower voltage.

edit: oh and those aren't my pictures. I just have them saved on computer from google.
« Last Edit: February 17, 2020, 07:03:52 AM by duckduckgoose »

Enzo

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #6 on: February 17, 2020, 01:24:16 PM »
I think you will find that which transistor you use as an output will have very little effect on the sound.  Solid state amps are massively fed back and are constantly "correcting" distortions they create.  The only overdrive would be to clip the thing.  And that isn't pleasant, contrasting a tube amp.  So unlike different brands and number on tubes in a preamp, swapping transistors doesn't usually get you anywhere.  I am sure those transistors will sound fine.

g1

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #7 on: February 17, 2020, 03:56:34 PM »
Agree with Enzo about generic output transistors, the '97 version used the standard (at the time) MJ15015 & MJ15016

https://www.ssguitar.com/index.php?action=dlattach;topic=3545.0;attach=4902

duckduckgoose

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #8 on: February 18, 2020, 08:01:40 AM »
ah I see thank you for sharing

well I found what I was curious about. found a schematic from the 2012 rg 80 and its different. seems they changed up the power output because of those expensive old school transistors. I think there also could be more labor involved mounting the older ones. I assume this is the same thing for their other amps power section just more power.

edit: oh the person that posted it on the other forum was also named g1. lol small world
« Last Edit: February 18, 2020, 08:07:21 AM by duckduckgoose »

g1

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Re: Randall rg-80 rg-100 power amp transistors
« Reply #9 on: February 18, 2020, 02:42:07 PM »
Yes, this is the newer made in China schematic.  Again, the power transistors are changed, but it should not have much impact on the sound.
I do notice that they have not used the current feedback scheme in this newest design (speaker (-) now grounded), some would argue that this will make a significant difference.