A new 12 000 - still working - update

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ReidarNikolai
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Re: A new 12 000 - mainboard problem

Post by ReidarNikolai » Fri Sep 18, 2015 12:52 pm

With the little knowledge and experience about how this works I am trying troubleshoot a bit on my own.
I have more than 500Vdc going into the 8,2k 2W - that is from the power board. On the other side of those 2 2w resistors I have the voltage drop mentioned above -going to the F1 on the chassis and to the 1W10k. After the 10k 1W next to the Erie on the main board I have Zero voltage. I have on the side with the turret but nothing on the side going to cap/V2/1W10k.

If this helps anybody to help me - please :)?

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neikeel
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Re: A new 12 000 - mainboard problem

Post by neikeel » Sat Sep 19, 2015 11:55 am

I presume you mean by F1 cap that is the PI filter cap mounted on the corner of the chassis up top.

You need to check that this cap is wired correctly with a good ground. If it is wired back to front or is shorted internally you will be dropping all your volts here and blowing the mains fuse with too much current.

That would explain your problem.
Neil

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Re: A new 12 000 - mainboard problem

Post by ReidarNikolai » Sat Sep 19, 2015 4:22 pm

Hi Neil and thanks a lot for chiming in here..

The cap on the chassis is a TAD 32uF.
You say: "wired correctly and with a good ground"
I might have missed something here.
There are only two cables on the can:
A black on the "tip" with no color that goes to Larry ground point 2 or 3 - I am not in my basement right now.
A blue on the red "tip" that goes to the 10k2W on the mainboard

Neil: you also say; "If it is wired back to front or is shorted internally" - how do I check this?
Maybe the easiest way is just to change the PI filter cap - I have a spare TAD and also a F&T laying around.

What do you think?

BTW I am not blowing any fuses at this point.

Thanks again
Reidar
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neikeel
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Re: A new 12 000 - mainboard problem

Post by neikeel » Sat Sep 19, 2015 5:28 pm

But I must have misread you were blowing fuses before?

Try a different PI cap. IMO 32uF there is too low. 48/50uF is minimum and 64uF or 100uF better,
Neil

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Re: A new 12 000 - mainboard problem

Post by ReidarNikolai » Sun Sep 20, 2015 4:47 am

Thanks Neil

I did blew fuses at a time. I connected the center tap to the diodes and the first Erie - instead of between the Eries..

The reason for using the TAD was that it was or is in Georges parts list for a 12 000.

I have both a Sozo and Erie 100 as well as F&T 50+50 - I´ll try the last one first.
Will try to change it this afternoon and report back :)

Thanks
ReidarNikolai
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Re: A new 12 000 - mainboard problem

Post by ReidarNikolai » Sun Sep 20, 2015 7:57 am

Took away the TAD and put in a F&T 32+32 - same. about 150Vdc when I flip stand by - then voltage drop..

Next thing to look at is maybe the preampcap?

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Reidar
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Re: A new 12 000 - mainboard problem

Post by Carbia » Sun Sep 20, 2015 10:07 am

Check it on stages, I mean:

Unsolder all the positives of the electrolytic filters except the mains. Check if the voltage is fine.
Solder the screens filters and check voltage again.
Solder the PI filter and check the voltage again.
Solder the preamp filter and check again.

In that way, you will know, for sure, where is the problem.

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Re: A new 12 000 - working (finally)

Post by ReidarNikolai » Mon Sep 21, 2015 2:49 am

I love the smell of electric components working hard in the morning :)
It´s 9:30 in the morning - I have already had 45 minutes with the amp loud - really fun amp to play.

So it was the Erie preamp filter that was faulty.
I will get myself another.

For now it has Mullard reisusses in V1, V2 and V3.
Sino EL34´s biased to a bit under 30mA - will put in EH6CA7 later today.
I will put in NOS pres when the amp is a bit more settled.

Still need to decide if I want that bright cap or not - it seems bright enough.

Thanks Carbia and Neil for guiding me along.

Thanks
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Re: A new 12 000 - working (finally)

Post by neikeel » Mon Sep 21, 2015 3:59 am

ReidarNikolai wrote:I love the smell of electric components working hard in the morning :)
It´s 9:30 in the morning - I have already had 45 minutes with the amp loud - really fun amp to play.
So it was the Erie preamp filter that was faulty.
I will get myself another.
For now it has Mullard reisusses in V1, V2 and V3.
Sino EL34´s biased to a bit under 30mA - will put in EH6CA7 later today.
I will put in NOS pres when the amp is a bit more settled.
Still need to decide if I want that bright cap or not - it seems bright enough.
Thanks Carbia and Neil for guiding me along.
Thanks
ReidarNikolai
The term bright cap in this amp is a misnomer, it is no such thing!
It is a bypass cap for the lead channel volume put that helps bring in some of the gain at lower volumes. I have found that on older amps the 5000pF cap (with 60s/70s Mullard pres and Mullards xF2s)is very smooth but adds an extra bite, newer amps (stiffer with new caps and new production tubes etc) can be a bit harsher.
It really depends on how you use your amp. I prefer my amps with them, I find the amps can be a little dull at lower volumes if you want a clean zone with a bit more sparkle then use a 100pF cap (now that is a bright cap, and a 500pF is a bright spikey cap IMO!).
Neil

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Re: A new 12 000 - working (finally)

Post by Carbia » Mon Sep 21, 2015 5:14 am

I have mine ('71 SL) without it, but usually use a 100pF.
Adds a little bit of crisp at low volumes.

But, ir you're going to run the amp flat out... it doesn't affect :)

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neikeel
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Re: A new 12 000 - working (finally)

Post by neikeel » Mon Sep 21, 2015 5:21 am

Carbia wrote:I have mine ('71 SL) without it, but usually use a 100pF.
Adds a little bit of crisp at low volumes.

But, ir you're going to run the amp flat out... it doesn't affect :)
I find up to 8 it does (I actually like 6-8 best as you can get some clean tones!)

Listen to Georges clips with the bright cap switch of his 12 series.............
Neil

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Re: A new 12 000 - working (finally)

Post by Carbia » Mon Sep 21, 2015 5:49 pm

Yeah, I know, but I mean running up to eleven :mrgreen:

I have the '71 without it because the amp runs very fine with my guitars at 6-7. I tried some bright caps, but finally, I decided to go without it. (I have to say that my guitars are bright... strats and gibsons with minihumbuckers :wink: )

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Re: A new 12 000 - still working - update

Post by ReidarNikolai » Wed Oct 14, 2015 4:52 pm

Been a couple of weeks :)
The Erie filter cap appeared and is installed. Works.
I realized that the tone section wasn´t working - forgot a cable or two.
Sounded good anyway :rock:

So today I tried to install the 6CA7´s today but I have a bad quartet - the difference between the hottest and the coldest when I install them is more than 15mA.
I don´t know if there is any meaning returning them to TubeDepot - it cost just as much as buying a new set.

For now I am happy with the noName Chinese EL34 I bought from TubeDepot.
Still Mullard RI in V1, V2 and V3 - CV4004x2 and a 12AX7

Pictures to come when I get the amp out in the sun :)

Thanks
ReidarNikolai
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Carbia
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Re: A new 12 000 - still working - update

Post by Carbia » Wed Oct 14, 2015 6:19 pm

Living in Norway, buy tubes from Tube Town germany. Good matched tubes :rock:
for the preamp, try to get at least one vintage Mullard. This is a good seller: http://www.ebay.es/itm/381429253002

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Re: A new 12 000 - still working - update

Post by ReidarNikolai » Thu Oct 15, 2015 2:11 am

Thanks Carbia - will check out both :)

ReidarNikolai
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