[Songforyou]

Glad to hear the EH EL84s get another recommendation for the Scott.

Two questions regarding my Scott:

Rectifer tube: Mine goes periodically.  How periodically?  More frequently than my EL84s.  What could cause this?  My unit does see several hours of daily use, but shouldn't a rectifer outlast the output tubes?  I can't even think of a Mullard at the rate I replace them.  Glad the Sovtek is only $15!

Headphone: Mine is noisy.  I can tell it has potential, but the hum increases with the volume.  Cause?

I'm hoping Hot Glass can chime in.  Speculation is welcome.

Thanks!

[Sea-Bee]

  Hi Ryan!

It is Sea-Bee from the HH Scott"s secure forum!  Good to hear from you!!

It sure has been a while.  I cherish thos brass knobs for the set too!  Brasso.

Yes, everyone has their favorite tubes.  I've been fooling around with them is HH Scott gear for over 30 years.

(My all time favorites) the ones in current production, or readily available.

Amperex 5AR4 or a NOS phillips 5AR4
JAN Phillips 6U8A (phase splitter)
Sovtek El84M (6n14n-EB) military grade.  "Tough buggers"
JJ Electronics (Tesla) ECC803 gold.  "quiet and smooth"

Ryan, we are still using the same old LK-48 (222-D) amp since 1999 with little trouble.  TNX to your kindly advice.

It has since been recapped Bias-filament and B+.

You sure can't beat a HH Scott amp when it is running sweet.

Be cool,
Sea-Bee

[Sea-Bee]

Her[/size]e is a real stocking stuffer MERRY CHRISTMAS!!

Study this!!  Take this link and you will really dig this!  http://antiqueradios.com/forums/viewtopic.php?t=35883&highlight=

I used four Tiacon 100MFD@100V elecrolytic capacitors hot glued together with the positive leads tied together and soldiered to the common "can" lug.  The negative leads went to all four lugs.  I used a 1/16 drill accomplish this, drilling through the terminal plate.

It got pretty involved, but hey...what do you say? 

If you get in a real SNARL pulling the old capacitor out of the can, get a pan and boil the can for five minutes...out it comes with a corkscrew.

Happy Holidays!!

[Brett Buck]

Two questions regarding my Scott:

Rectifer tube: Mine goes periodically.  How periodically?  More frequently than my EL84s.  What could cause this?  My unit does see several hours of daily use, but shouldn't a rectifer outlast the output tubes?  I can't even think of a Mullard at the rate I replace them.  Glad the Sovtek is only $15!

   I would expect that the same trick used for the ST-70 will work - 1N4007 diodes in series with each rectifier plate.
   
     Brett

[Sea-Bee]

Hello to Songforyou,

NO, TO THE DIODES IN PARALLEL WITH THE 5AR4 tube!  The start is too harsh and would wreak havoc with with the tubes.  Tried that, been there.  Please do not do that.

I had the same problem with my rectifier tubes going out periodically, with a 120hz hum that increased with the volume.  Self-same problem as yours!

Did your replace all of your can caps in your B+ (high voltage) circuit yet?  When I did, the problems with the 5AR4 tube going kaput pretty much stopped! Iv'e had the same Amperex 5AR4 tube in my set for the last 11 years, and it is still going strong.

To explain in brief: When one of your sections of your multisection caps go to low-Z (in the process of shorting out); the stress on the rectifier tube becomes more than it can handle.  Kaput rectifier tube.  The residual hum you hear (well, most of it) is from a can going bad.

My suggestion is that you bench your amp and replace BOTH OF YOUR B+ cans right away.....and for fine measure, restuff your heater/bias can with new caps. 

I'll be around to help you out if you have got any questions.

[Brett Buck]

Hello to Songforyou,

NO, TO THE DIODES IN PARALLEL WITH THE 5AR4 tube!  The start is too harsh and would wreak havoc with with the tubes.  Tried that, been there.  Please do not do that.

   I said SERIES, which precludes the problem you are screaming about.

     Brett

[Sea-Bee]

That is OK! sorry!  We learn, we move on.

I've heard of many folks in the past doing the same thing for decrease of IMD, and also  some have inserted silicon diodes to isolate the various stages of the B+.  I can see the your logic here; very sound indeed.   

[Brett Buck]

That is OK! sorry!  We learn, we move on.

I've heard of many folks in the past doing the same thing for decrease of IMD, and also  some have inserted silicon diodes to isolate the various stages of the B+.  I can see the your logic here; very sound indeed.   

  Well, I certainly didn't think of it - I heard about it in regards to the Van Alstine U70, and I think they got it from Kevin at Dynakitparts (very highly recommended, great stuff and great people).

    Certainly you don't want to replace the rectifier tube with a diode rectifier (which is what parallelling it with a diode would amount to) without a delay circuit or some sort of "softening" for exactly the reason you note. It will work but be very rough on the rest of the parts.

     Brett

[Sea-Bee]

Hi Folks!

Are you annoyed by that elusive HUM that you hear from your HH Scott Tube amps after you have replaced all of your B+ cans and gone the 6U8 route??  It is the Filament/bias can that IS at fault

Well, my set IS running really superbly with very little background hum for the last year.

I restuffed the POSITIVE can capacitor with new ones.  It gets pretty involved here, but you WILL relish the outcome and thank yourself that you did.

Here is a link to follow http://antiqueradios.com/forums/viewtopic.php?t=35883&highlight=


Good luck guys and dolls

[Hank]

I've bought three 222-C units off eBay and I still have my LK-48B that I bought and built at about age 16.  I have re-capped one of the 222-C's, except for one electrolytic multi that I have.  I also plan to replace the selenium rectifier with a diode bridge and replace the follow-on resistors to lower the voltage voltage back down to the level that the selenium output (you all have done that mod, right?)  You just can't beat the sound of these over-engineered Scott integrated amps without spending a fortune.  BTW, I also bought two Scott tube tuners - a 350 factory unit and the kit version (I think the model is LT110).

[Sea-Bee]

Yes, they are excellent sets.  To say the least!

Hey do not forget to restuff the POSITIVE common heater/bias cans on your amps.  I had to restuff mine last year.  What a difference that made.   Just to play it safe, you should do this along with replacing your low voltage bridge rectifier too with a silicon bridge recitifier too.

I've given it much thought on your losing your 5AR4 tubes so frequently...... It did happen to me on my 299-C until I replaced all of my B+ cans (high voltage cans).  When an old can multicap goes bad it frequently shorts and drags down the B+ voltage to the point of blowing the 5AR4 tube (or worse FRIES your power transformer).  Give this issue some thought.  I'll be around.

[Sea-Bee]

Just purchased some genuine NOS TESLA tubes

1. NOS TESLA ECC803S gold pin.

2. NOS TESLA  ECF82 (6JW8) to replace-update the 6U8A tubes (phase splitters).  This really quieted things down alot!!!  LOOK OUT FOR THESE BUGGERS AND BUY THEM!!
 
With these tube amplifiers, you are always on the learning curve and willing to try new things.

Keep on the lookout for NOS TESLA tubes (watch out for counterfits, fakes)

Clifford

[Hank]

Hello again, Sea-Bee, from this former Army guy.  I haven't bought tubes in a long time.  What's the source of your new Tesla's?

[Sea-Bee]

I found my sources on eBay.

http://www.jacmusic.com/JJ/803S-FAKE/index.html

The NOS Tesla tubes were made in the former Czechoslovakia

http://www.ebay.com/itm/PAIR-TESLA-ECF82-/150879359585? pt=Vintage_Electronics_R2&hash=item23211c5261

Never really cared for the durabilty of Ei tubes, or even the sound of them (my wife detests them!). 

I do like Reflektor-made 6n14n-eb tubes for outputs (Sovtek EL84M)

http://www.ebay.com/itm/4x-MATCHED-GOLD-GRID-6P14P-EL84-NOS-80s-Tubes-QUAD-/300766790013?pt=Vintage_Electronics_R2&hash=item460719017d

These tubes really great!!

[Hank]

Thanks for the links, Sea-Bee!

[Sea-Bee]

Heyy,....gotta' help a fellow veteran, and anyone else from being shafted!

Still, it is all up to you...

Ie.  When I blew a dog whistle HARD in the the house, my wife clapped her hands to her ears and shouted..."STOP IT!.  It hurts frickin my ears!  The cat darted under the couch because of the awful noise.

So, from that time on.....I would ask her if our set sounded any better, or asked her to listen for a particular noise that I heard too.

Yep....she could not stand the awful high-end racket that the Ei tubes gave off (also they had a bit of low-end microphonics).

With her help we settled on these tubes for being smooth and being of an exellent frequency range.

JJ TESLA ECC83 (gold pin) for both the phono and the AF stages  very nice tubes

NOS TESLA  ECF82 (drop-in replacement for 6U8A) very quiet low hum, and very good frequency coverage.

Sovtek EL84M   output tubes  (matched quad).

She loves her LK-48.....I love the end-results!!

Cliff


 

[Sea-Bee]

New album and pictures of my capacitor restuff


Please search my albums to find them.

You'll just love em'........ Chow down!!

[Hank]

Sea-Bee, you really "uncorked" that can cap.  Where there's a will, there's a way.

[Sea-Bee]

Done this more times than I can remember!

Firstly, I replace ALL can Electrolytic filter caps.  Restuff the Positive common filament/bias can... and replace all high voltage cans too... no exceptions when you are working on a customer's set.  Yep the coupling caps (high performance ORANGE DROPS) too "next higher voltage up"  (If it is a 250V cap.... up it to 350-400V)  a wee bit larger .

Just finished a project 299-D amp .... When I first saw it's 7591 output's plates were all glowing red-orange yikkkes!  And all of the 12AX7 tubes were dark.  

It was the biasing circuit at fault, and the front-end tubes were not glowing as they should.  Yep, the positive "can" shorted.  Did the usual... "recanned" the unit and replaced the bridge rectifier too.  Replaced all the outputs with JJ-7591 and rebiased the grids... *that is another tale*  Happy amp.... Just "Foosed" his amp!!