Where to find 6000uF 50V replacement cap cans??

[RG100ESROX]

Hello everyone!

I've been trying to find a couple of 6000uF 50 volt electrolytic caps for my RG100-ES, but I cannot find them anywhere.

Based on photos I'm assuming these cap cans are about 37mm to 40mm diam. cans??

If I cannot find 6000uF. Do I want to go little below or a little above the original 6000uF filter cans? Also, what would the impact be on tone if I were to go a little over or under the original 6000uF caps? I'm assuming that any voltage rating above the original 50 volts is acceptable?

Thanks in advance to all that reply.

-J

[Tassieviking]

As long as a new cap is 50V or higher you can use them, I sometimes get a higher voltage cap so it fits the mounting hole of the cap I am replacing. (caps have gotten smaller over the years)
You could try Mouser, Element 14, DigiKey, etc.
I would measure the lead spacing and then look for a 6000uf (5000uf- 7000uf) capacitor that will fit the PCB board, most likely it will be well over 50V.
Cheers
Michael

A picture would make it easier to give you better advice.
If you tell us where you are someone might even know a local place near you.

[g1]

Common values would be 5600 or 6800uF, either should be close enough.  And 63V would probably be more common.

[RG100ESROX]

Thanks for the replies.

Here is pic I found online (since I wasn't smart enough to take some while I was at it.)

The cap in the photo appears to be about 35mm if I'm not mistaken.

I did find a couple of 35mmx70mm 100V 10000uF caps in my forgotten stash. Is there any reason I would NOT want to use a 10000uF cap in the power supply positions??

Thanks in advance.

-J

[RG100ESROX]

Well, I was able to find a couple of 6800uF caps that are 100 volts and measure 35mmx70mm on Amazon for a whole $9.95 for 2pcs.

However, I would still like to know what the advantages or disadvantages would be if I used the 10000uF filter caps in the power section.

I'm assuming maybe a little bit better and tighter bass response if anything??

Thanks again in advance.

-J

[g1]

Yes, a bit stiffer response if it is even noticeable.

[RG100ESROX]

Well, if they come with just a tab bit tighter bass response, and I mean just a tad. They will be perfect.

Now, I'm familiar with the effect and feel of caps on a tube amp, but on a SS amp...not so much.

What would slightly smaller caps do to my tone and feel?? Say, 4700uF or so...

I'm assuming with the SS amp that a lower cap value may not result in a pleasant sag in my tone...or am I wrong??

[RG100ESROX]

Hey guys??

It shows one of the HT filter caps with its + to ground. Is this correct??

If so, which cap is it with + to ground??

[saturated]

I'm gonna say yes it's correct as it looks like a bipolar power supply but we better wait for verification

And I would think it is the capacitor on the left

[RG100ESROX]

I'm gonna say yes it's correct as it looks like a bipolar power supply but we better wait for verification

And I would think it is the capacitor on the left

You are correct. I followed the schematic back to the HT caps, and it was in fact the cap on the left. Now that the issue with the caps has been remedied. I'm having issues biasing the amp.

Based on a thread here in the forum. I should see 40/50mA across the two .6 ohm 10 watt resistors. However, I'm only seeing as high as 20mA with the bias pot nearly dimed clockwise.

However, it doesn't seem that the amp sounds like it should regardless of where I set the trim pot.

What am I missing here??

Any bias experts here in the forum regarding the Randall RG100-ES??

[Tassieviking]

C39 has + to ground, the - side goes to the -40V supply rail.

Think of the power supply as 2 batteries in a torch, ground is where the 2 batteries touch each other in the middle, then you get a -1.5V and a +1.5V as well as the middle ground at 0V.

Or else think of -20 degrees is lower then 0 degrees so 0 degrees is hotter then the -20 degrees.

I am terrible at explaining things.

[RG100ESROX]

No. That was perfect. I totally got the battery analogy. Thanks for the clarification.

But, I'm still left with an amp that doesn't sound like it should, and I may be trying to bias this thing incorrectly.

Am I supposed to be reading the voltage drop across the two .6 ohm 10 watt resistors? If so, what is the correct bias reading range I should be seeing?

And also, why does my amp not sound correct no matter where I set the bias trim pot. It used to sound just like the tone in the Dokken 'Just Got Lucky' (guitar only) video.

Video---> https://youtu.be/Jl9Oqgzv0fU?si=lJBaMxde4CvG9Yew

But it doesn't anymore for some reason. It's kinda flubby...and too round sounding (the 10000uF HT FILTER caps didn't change anything.)

Anyone have any ideas what might be going on here???

[phatt]

I think you have made a false assumption that the power amp is at fault.
Larger caps won't do anything, you would only improve that with a bigger Transformer as that defines the power not the caps.
Far more likely the issue is in the preamp stages.
Also have you upgraded your Pickups to hotter ones?
Have you added Changes to any pedal board setups if used?
Any of the above would likely cause the problems you have.
A very common issue that can cause loss of power is corroded Efx loop sockets.
Channel switching circuits could be failing,, any contact points could be corroding causing signal loss.

As for biasing the power amp, I'll assume you do not have a scope?
To get very close turn off ALL distortion, you want a pure clean signal to hear this trick.
Volume up just enough to hear it with your ears close to speaker.
Now just pluck one string and let it ring out.
If bias is not correct you will hear a slight buzzing sound with the note. It sounds a lot like a torn speaker cone. Now gently adjust bias until the buzz just disappears.
Depending on the design you may not be able to make it perfect.

without more detail and a schematic it's hard to know what maybe causing your problem.
Phil.

[RG100ESROX]

First off...thanks for the in depth reply.

As far as the HT filter caps are concerned. I never assumed they would give me any additional power. That would be absurd. (-; I was wondering if they might tighten up my bass response a little. Nothing more.

As for the amp. I'm not running any effects. The PUP I'm using is about 16K. The speaker I'm using is straight out of one of the 4x12 Randall cabs that came with the amp. Which is a G12M-70. I'm also using a V-30 that improves the tone a bit.

With regard to the biasing of the amp. I've read in a few posts here in this forum that the way you bias these amps is by measuring the voltage drop across the .6 ohm 10 watt resistors. There are two of them. It would be nice if someone could confirm this method for everyone.

I have my doubts about the bias method posted in this forum. The reason why is, I measure anywhere from zero volts with the trim pot turned counter clockwise, and as high as 25mV with the trim pot about noon, one o'clock position. The instructions say to bias the amp up to 40/50mV. The problem is, mine is only going as high as 25mA. So, I don't really think this is the correct biasing method.

I do have a scope. Which I am not completely proficient at using yet. So, if someone would like to give me some detailed instructions on how to use it to bias my amp correctly. I would be forever grateful.

Anyway, any suggestions/instructions would be greatly appreciated. I would really like to learn how to bias my amp the correct way.



-J

[phatt]

If the instructions say 40/50mV across those resistors (sounds about right) and you can only get 25mV then there is a fault in the Amp "Not the instructions".

BTW,
Additional power is how you get tight bass that does not flab.
That is why bass amps are 4 or more times the wattage of guitar amps.
They have to have much bigger transformers to deliver the same "Clean" SPl at low Freq as a 40 watt guitar amp at higher freq.
Freq below ~200 ~ish hZ chew up heaps of energy.
Phil.