How to bias a Rivera Rake Reverb + tubelayout

[vinni]

Hi,

I want to know where the bias-pot is in this amp / how to bias the Rake.
Also....what is the tube-layout of the preamp tubes?

B.t.w. I think it still sucks that you cannot contact Rivera by Email! :mad:
I don't live in the USA....so it's expensive and when he's open I'm asleep...
Customerservice.....

Vinni

[teefus]

there used to be a biasing FAQ on rivera's website. i think most if not all riveras have the bias pot on the pc board, kind of in the middle/back near the power tube area. on my bm60 head, you pull the chassis partly out of the cabinet to access everything. disconnect the speaker lead (riveras have a disconnecting jack), turn the amp on and let it warm up. FOR EL34's (which i think the rake uses, iirc) once warm, set your meter to mvdc, flip the standby switch to on and put the red lead on pin 8 of a power tube and the black lead to a chassis ground point. set the bias pot for 37-40mvdc. again, these instructions are for riveras that use el34's.

[vinni]

Hi T,

So.....correct me if I'm wrong....

But there's no need to connect a speaker to the head?
And you can flip the standby switch to on without causing any
damage to the tubes or OT?.....Hmm....
I always thought there has to be a load connected...

Vinni

[78tsubaki]

Teefus is correct. The bias pot is in the "motherboard" (main circuit board). Mine is blue and very easy to see. It is located near V5 just read the board.

THERE WILL DEFINATELY BE LETHAL VOLTAGE PRESENT! TAKE YOUR TIME AND STUDY THINGS BEFORE YOU GET INTO HARMS WAY.
If you dont understand this fact please find a tech to perform this work.

Like Teefus said something that I found helpful was that because of the disconnecting jack for the speaker you are able to take your measurements at the Jack #1 terminals. You are summing the totals as you will see below.

Straight out of the Rivera Instructions.
"Observe the two wires connected between the output tube circuit board and the speaker jack board. These wires carry the output cathode current.
Connect your current meter across the pads to the speaker jackboard where these two wires are soldered to.
Make sure that nothing is plugged into speaker jack #1. Place an appropriate load on speaker Jack #2 if this is possible. If not, you will be ok as there will be no signal present." (I just plugged my speaker into Jack #2 but not necessary to do so.)
"No signal of any source should be plugged into the front panel input jacks or the rear panel effects loop jacks." (No guitar or effects.)
"Turn the amp on. Make sure that the High/Low Power switch is in the "High" position,and the Standby switch is in the "On" position.
After the tubes warm up, observe the idle current. For 55 versions (2 output tubes), adjust for 80 to 90 MaDC. For 100 Versions (4 output tubes), adjust for 160-180 MaDC. The actual setting you choose will depend on the particular tubes used and their gain. For example, a really high gain EL-34 should be bised colder (40 MaDC per tube) than a low gain tube which may sound best run hotter (45 MaDC per tube)."

I hit around 88 MaDc on my Jake and it sounds great with Winged Cs installed. The High/Low power switch may be labeled Vintage/Modern. Use the Modern setting.

All info in "" comes straight from Rivera. Super people super company and rock and roll products. I am receiving no money for this info so I hope I don't offend anyone from a copy right point of view. I would never want to offend the Paul and the crew.

Use extra care not to allow your meter leads to touch anything but the terminals that you are measuring. DC to ground = ouch or worse.:nono

Remember to turn off the amp and be extra careful when reinstalling the chassis. I usually unplug mine and let it cool all the way down.

The tube positions are clearly shown in the R55 manual. Used to be able to get that on line as a PDF.

[teefus]

ooops. i forgot about the triode/pentode and hi/lo power switches. thanks.

[78tsubaki]

YOU ARE RIGHT! This method is only for biasing most Rivera amps.
For all other makers you need to follow their instructions and that usually includes having a speaker load applied everytime you come off of standby.

Riveras are different. :AOK Paul and Co. provided additional protection via a speaker jack circuit that opens the circuit preventing a signal from being present unless a load is applied by jacking in a speaker or another load. That is also why you can measure the MaDC at the two wires on the seaker jack board as described.

If you have a speaker plugged into Jack #1 on a Rivera you will not be able to get you reading at that test point.

Pretty nifty. I am uncertain as to why they do not require but recommend that you apply a load to Jack #2 unless in the off chance that the protection circuit in Jack #1 fails to do its job.
I have never had a problem biasing my Jake using this method.

[vinni]

Thanks guys....

The reason for asking is that I don't have a manual and like to try different
powertubes. I've got JJ EL34LS, Svet's C-winged EL34's and really like to try the Groove Tube KT77. Any other recommendations?

I also like to experiment with the preamp tubes.
So I have to know the tubelayout....
What tubes do you guys use?
I heard/read that the NOS Tesla's do sound really good in the Rake.

Vinni

P.s. is it MaDC or MvDC?

[vinni]

Stupid question....

For safety....can't you used wear a pair of rubber gloves?

Vinni

[78tsubaki]

It is MaDC on these amps. No conversion necessary.

I have only used original equipment Rivera re-branded and the winged C EL34. I heard that Rivera used to use Siemens but they got harder to find in quantity.
I think Mike at http://www.kcanostubes.com/content/ would have some great suggestions.
My Jake is tubed with tubes that I bought from him while I was living in Japan. Very trustworthy and great service.
I am using a Mullard in V1 and a Brimar in V2. Original Chinese 12ax7s in V3-5.
Check out http://bellsouthpwp.net/r/i/ricjohns/Rivera%20Power%20Tube%20Guide.htm

That link came from the old Rivera Forum and still has some interesting info. The Biasing link in the thread no longer works. The info I sent to you earlier came to me directly from a fax from Rivera. Same info.
Cheers

[vinni]

Hi guys.....

Well I've got two NOS matched Siemens EL34's from KCA.

There is some info on he boxes :

Tube 1 : PC 40.7 TC 5450
Tube 2 : PC 41.0 TC 5390

And " Matching current 36"

So what does this mean?

And I don't have any figures on my Svets.....Is that a problem?

Vinni

[vinni]

Bump.....

Vinni

[Blue Strat]

Hi guys.....

Well I've got two NOS matched Siemens EL34's from KCA.

There is some info on he boxes :

Tube 1 : PC 40.7 TC 5450
Tube 2 : PC 41.0 TC 5390

And " Matching current 36"

So what does this mean?

And I don't have any figures on my Svets.....Is that a problem?

Vinni

Those are test readings used by my supplier and myself to group tubes into matched pairs. They mean nothing to the end user unless you're trying to replace those tubes with more tubes that match.

Set the bias in the low to mid 30mA range unless you know the plate voltage in which case, calculate and use 60% idle dissipation.

[vinni]

Those are test readings used by my supplier and myself to group tubes into matched pairs. They mean nothing to the end user unless you're trying to replace those tubes with more tubes that match.

Set the bias in the low to mid 30mA range unless you know the plate voltage in which case, calculate and use 60% idle dissipation.


Hi Mike,

Thanks....but the mid 30mA confuses me because higher up in this topic there's a quote from the Rivera manual saying to bias in the 80-90mA range.
:confused:

And....how do I calculate Plate voltage?......

(ok....I'm a n00b regarding biassing.....but you've guessed that already :AOK)

Vinni

[Blue Strat]

You don't calculate plate voltage, you have to measure it. It's probably safe to assume 450V and you'll almost never be off by more than 10%...usually less...and the tubes don't really care that much about 10%.

I don't know where 80-90mA is coming from unless that's a combined reading of both tubes. You can check with Rivera on that one.

[vinni]

Ok thanks....

I finally found the email account of Rivera somewhere so I dropped them an email.

Thanks again!

Vinni

[aleclee]

You might find this page generally useful: http://bellsouthpwp.net/r/i/ricjohns/Richard's%20Rivera%20Amplifier%20Page.htm

[vinni]

Hi Alec,

I know these pages...
But the link to the Bias-page doesn't work.

Vinni

[vinni]

Well,
No news from Rivera.
I'll guess I have to take the gamble

Wish me luck!

Vinni

[vinni]

Well....I've done it! :D

I've biased the Siemens tubes at around 73mA.
(2 X 36mA like Mike suggested)
Higher did not sound better. Lower choked the sound.

So what's the verdict?
They sound more open, sing more (woman tone)
Was it worth it? Yes....but I had hoped for more.
I compared that amp with my other Rivera Rake.
There were certainly differences, but not that much.
Maybe a good PI and preamp tubes will get me there.

Vinni

[aleclee]

The reason for asking is that I don't have a manual and like to try different powertubes. I've got JJ EL34LS, Svet's C-winged EL34's and really like to try the Groove Tube KT77. Any other recommendations?

I also like to experiment with the preamp tubes.
So I have to know the tubelayout....
What tubes do you guys use?
I heard/read that the NOS Tesla's do sound really good in the Rake.I like 6CA7s instead of EL34s in my Rake. It makes for more Fendery clean tones but the drive channel sounds less Marshall-like (but in a way that works for me).

As for preamp tubes, I haven't found anything that I like better than the 9G Chinese tubes that were original equipment. I've tried a bunch of NOS tubes but they just don't sound as good to me.