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PostPosted: Sun Apr 22, 2018 6:02 pm 
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Hi all,

I am going to restore my Dynaco MKIII and would like to get matching tubes. My MKIII's are different generations, one has KT-88's, one has 6550s; different generation capacitors, etc. I will be replacing capacitors, switches, etc.

Where I need help is ID'ing the tubes on them, if possible. I can and will take more photos as required.

1). One has Russian Svetlana 6550 tubes, the other has Chinese Valve Art KT-88. The date code on Svetlana tubes is 0106. I would like to get a pair to match these. Are these the "winged C"?

2). 6AN8 tubes - one has a tube marked Marconi Radiotron MH; the other has Rogers 6AN8A Canada. Which one should I get to match the other?

Thank you.

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PostPosted: Mon Apr 23, 2018 2:04 am 
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Location: Fairport Beach (in Pickering), ON, CA
zhenya01 wrote:
Hi all,

I am going to restore my Dynaco MKIII and would like to get matching tubes. My MKIII's are different generations, one has KT-88's, one has 6550s; different generation capacitors, etc. I will be replacing capacitors, switches, etc.

Where I need help is ID'ing the tubes on them, if possible. I can and will take more photos as required.

1). One has Russian Svetlana 6550 tubes, the other has Chinese Valve Art KT-88. The date code on Svetlana tubes is 0106. I would like to get a pair to match these. Are these the "winged C"?

2). 6AN8 tubes - one has a tube marked Marconi Radiotron MH; the other has Rogers 6AN8A Canada. Which one should I get to match the other?

Thank you.



Do you have a good tube tester? If not:

1) Buy 2 matched pairs of Gold Lion KT88's

2) Go to eBay and buy a matched pair of 6AN8's and keep the others for spares

If you really want to make these amps sing, get a pair of these boards and forget about the 6AN8's:

http://store.triodestore.com/diytubemk3.html

I did the 5751 & 12BH7 combo. You will be astounded at how good these amps sound! Shhh :wink:

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Collecting vintage tube Pilot (Pilotone) HiFi gear.


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PostPosted: Mon Apr 23, 2018 5:39 am 
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At this time, I'm only interested in getting my MK-IIIs the most important updates to get them running, rather than upgrading them. I'm replacing all capacitors, switches, etc. Even these basic changes is going to cost me $250 without tubes.

I already have 3 sets of KT-88s / 6550, so if I can find a matching pair to this SED Winged C, at least I can save myself 150-200 dollars. I will probably buy a matching set of 6AN8's, but it would be cool to find one matching to the ones that I have - I have four, and they are all different lol - Marconi, Rogers, Zenith and GE.


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PostPosted: Mon Apr 23, 2018 6:36 am 
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I gotta agree with tom.

However....if money's tight why not just run what you have til they're cooked? Then retube properly and go matched pairs n quad

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PostPosted: Mon Apr 23, 2018 8:01 am 
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Location: Waterdown, ON, CA
Tom_r wrote:
zhenya01 wrote:
Hi all,

I am going to restore my Dynaco MKIII and would like to get matching tubes. My MKIII's are different generations, one has KT-88's, one has 6550s; different generation capacitors, etc. I will be replacing capacitors, switches, etc.

Where I need help is ID'ing the tubes on them, if possible. I can and will take more photos as required.

1). One has Russian Svetlana 6550 tubes, the other has Chinese Valve Art KT-88. The date code on Svetlana tubes is 0106. I would like to get a pair to match these. Are these the "winged C"?

2). 6AN8 tubes - one has a tube marked Marconi Radiotron MH; the other has Rogers 6AN8A Canada. Which one should I get to match the other?

Thank you.



Do you have a good tube tester? If not:

1) Buy 2 matched pairs of Gold Lion KT88's

2) Go to eBay and buy a matched pair of 6AN8's and keep the others for spares

If you really want to make these amps sing, get a pair of these boards and forget about the 6AN8's:

http://store.triodestore.com/diytubemk3.html

I did the 5751 & 12BH7 combo. You will be astounded at how good these amps sound! Shhh :wink:


Zhenya.

Those Svetlana are infact the winged C versions. Take a closer look at the four 6an8's, they are more than likely the exact same tube with different labels.

As Tom mentioned. Updating the front end board on the MK 111's is far and away the biggest improvement you will ever make.
The 6an8 [a pentode section and a triode section inside] is a rather mediocre sounding tube to begin with and there are no other substitutes for voicing the amplifier.
Replacing the 6an8's and buying new coupling caps on the existing board is just a waste of time and money.
Do yourself a very big favour and take Tom's advice here..... look into the Triode store front end board or the Bob Latino front end board over at tubes4hifi.com. Either one will take your Mk111's to a whole nother league!
Either company allows you the option of tube choice for their front end boards. ecc82/12au7, ecc85/12ax7. 6fq7/6sn7, 12bh7. All of those tubes are common 9 pin dual triodes with so many examples to choose from.

Best of luck with your endeavor.


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PostPosted: Mon Apr 23, 2018 9:54 am 
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I do understand the benefits of the upgrades, but I am doing it step by step in terms of requirements to keep the amps running and the budget. So step 1 for me is to get them up to snuff. So I'm replacing all electrolytic caps, switches, and selenium rectifier / bias kit.

Next step would be to match all tubes, and then the upgrades may start - boards, individual bias, etc. I have had Dynaco for 15+ years now, and I love how were originally designed, and how upgradeable this equipment is. I totally restored 2 ST-70 amps in 2009-2010, and still have one of them. Next step for me is to get these MK-III's running, then I need to restore my PAS-3, which started humming (still all original). So it's all time and money, etc etc. One step at a time.

The main questions for me are:

1). Can I get another set of Svetlana winged-C to get the output "sound" the same?
2). How do I determine if my 6AN8 are the same? I realize that Rogers and Zenith didn't make their own tubes, so they may all as well be the same, but I have no idea. I may end up just selling all four vintage ones that I have and get a pair with matched pentodes and triodes.


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PostPosted: Mon Apr 23, 2018 10:10 am 
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Since you basically have no idea of the current state of your current tubes Burn em all up and then when they go replace them all properly

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PostPosted: Mon Apr 23, 2018 10:32 am 
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BinkyTheCat wrote:
Since you basically have no idea of the current state of your current tubes Burn em all up and then when they go replace them all properly


They all work fine and I think I have 2-year-old test result stickers still on them :). But you're right, I might do just that and see if and how they sound different. I'll throw in an extra pair of EH KT88 that I have and call it a day for now.


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PostPosted: Mon Apr 23, 2018 2:43 pm 
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If you are running the amps with any original e-caps in there you may want to save up for transformers too. 50+ year old e-caps are a hazard. At least change them before you run the amps. If any of your power tubes start to red plate you'll need to change the output caps too.

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PostPosted: Mon Apr 23, 2018 4:16 pm 
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Tom_r wrote:
If you are running the amps with any original e-caps in there you may want to save up for transformers too. 50+ year old e-caps are a hazard. At least change them before you run the amps. If any of your power tubes start to red plate you'll need to change the output caps too.


I put together a "kit" on dynakitparts and ordered the following parts already: new stacked electrolytic caps, new 2 electrolytic caps for each amp, new regular caps and bias resistors for each amp "just in case", new power switches and power cords, new bias kits (i.e. diode and resistors to replace the selenium rectifier and compensate for new resistance values), and new input connectors. Will also order new binding posts from tubes4hifi. That's my first stage of restoration. I'm already into major $$$s.

Then I will move onto matching tubes (hence this post), then may move onto upgrades (individual bias, heater supply rectification, board upgrades, etc.).


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PostPosted: Mon Apr 23, 2018 4:40 pm 
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That's a great start! I know it's not cheap to rebuild stuff.

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