Scott 222C

The 222C in my photo a few posts back came already wired for 6U8/6GH8 phase invertors. The 222C I am still working on is wired for 7199's. I rewired those sockets for the much easier to find 6GH8. It's just a matter of changing 3 wires on each of the two phase invertor sockets to make the conversion.

I don't know when Scott changed production on those.
 
Hey Guys,

Nice Find! I am still looking for somthing to wet my tube whistle but I thought this might be of help to you.

http://www.audioxpress.com/magsdirx/ax/addenda/index.htm

Their is a 4 part article that talks about rebuilding a 222C!

I haven't read the whole thing yet but it looks to be a wealth of information.

Hope it helps and good luck.

-r0n22

Excellent, r0n, thanks!! I'm downloading all the parts right now and will flip through them when I get this accursed fluid mechanics assignment done :sigh:

I've never actually seen this site before, looks good-- thanks for the heads-up!


*edit; I've upped all the PDFs here for all you other guys wanting to work on your 222C amps-- it's a really great series of articles with parts lists and lots of pictures!
 

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I enjoyed that 4 part story. But, keep in mind, you don't need to go that far to bring the 222C back to operational, and enjoyable, condition.
 
It came yesterday!! Been busy with school work however, so haven't had the time to open the box and look it over yet. :tears:

( :banana: :banana: :banana: )

Just to clarify, the bias supply doesn't benefit from ultrafast diodes, nor special caps with bypasses, or anything like that?

:scratch2:
 
You should open everything immediately and check for damage. Don't assume it wasn't used as a footstool for the guys stacking boxes in the truck. :rolleyes:
 
You should open everything immediately and check for damage. Don't assume it wasn't used as a footstool for the guys stacking boxes in the truck. :rolleyes:

Right-o

Quickly popped everything open-- it was triple boxed with foam in between each later and cut pieces to fit the amp snugly!!? This is THE BEST packaging job I've ever seen; I took a few photos along the way once I saw the packing job (bricktop, you should be proud!); simply outstanding! :thmbsp:

Nothing looks damaged and the box looked fine. This is one heavy sucker!
 
Well, then, you certainly got off easy without any freight damage.

To answer your question about the bias supply, considering the design and components available in the 50's, a simple silicone diode bridge rectifier IS a benefit from the original selenium rectifier! :yes:
 
Here is it! I pulled the knobs off right away to start cleaning them. The brass looks great and I can't wait to get 'er all shined up! Heavy as heck, too!!

I've had these tube socket inserts that I got off eBay (NOS, 20 for $8 shipped) and they look like they should fit; what do you guys all think?

Thanks Blast, I've got some bridges kicking around that I'll use in that case. I've read that silicon diodes are more efficient than selenium ones, and when they're switched that diodes (edit for the future; I meant to say resistors, been a long day... ) have to be added to cut off the higher voltages. I don't need to worry about that?


:banana: :banana: :banana:


Picture1348_sm.jpg


Picture1350_sm.jpg


Picture1351_sm.jpg
 
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Here is it! I pulled the knobs off right away to start cleaning them. The brass looks great and I can't wait to get 'er all shined up! Heavy as heck, too!!

I've had these tube socket inserts that I got off eBay (NOS, 20 for $8 shipped) and they look like they should fit; what do you guys all think?

Thanks Blast, I've got some bridges kicking around that I'll use in that case. I've read that silicon diodes are more efficient than selenium ones, and when they're switched that diodes have to be added to cut off the higher voltages. I don't need to worry about that?

Thanks for the photos! Don't worry about cosmetics or the socket inserts, for the time being.

Take the faceplate off and store it somewhere so it doesn't get beat up as you work on it.

First, with all the tubes out carefully check your AC voltages coming from the power transformer. You should have a pair of 360 volt taps at either pin 4 or pin 6 of the 5AR4 referenced to the grounded frame, a 50 volt tap (on the selenium bridge), a 6.3 volt tap for filaments and a 5 volt tap for 5AR4 filament.

Got all those? Then your PT is probably good.

Next, replace the bridge. Anything over 1 amp, 100 volts is fine. Remember to ground the positive output of the bridge.

Then replace the multi-stage 75/75/75/75uF (positive grounded) can with individual (100uF/100v) caps. Your can may be ok but, personally? I would replace it. I'm not a fan of 40 year old capacitors. Bend all the legs over on the original can to get them out of the way. Don't forget the bias voltage is negative. So you must ground the POSITIVE leads of all 4 caps.

Here's mine. Make your bridge look neater than mine by trimming the leads and use shrink wrap insulation:

20110615 HH Scott 222C adding 10 ohm bias check resistors 9 Copy.JPG

Those 4 resistors are all 20 ohm 1 watt. I would suggest 2 watt. The one-watters get kinda hot.

You said something about adding a diode? No, I think you mean an additional, or higher resistance resistor. There are several opinions on this. You could replace the very first resistor with a 33 ohm 5 watt... Since the new bridge runs more efficiently the 33 ohm will lower the voltage a bit more. But a higher bias voltage (which is why I suggest 4x 20 ohm resistors) is actually a little "safer" on the output tubes. Your call. You can always 'tweak to taste' later.

So you need your bridge, 4 caps and 4 resistors. Start there and we'll move on with power supply cap replacements, ok?
Brian
 
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Hi,

The 222C should have it's power supply capacitors and the bias power supply capacitors and rectifier replaced. You should also replace all coupling capacitors and plate feed resistors. This generally fixes about 99% of the issues in these amps and will make them reliable. If you do a web search, you can find places that describe exactly how to convert amps using the 7199 to use other tubes like the 6BL8 or 6U8. Newer 222C's actually use the 6U8. But the original configuration was with the 7199. The 7199 is a good tube, the real problem is that it is just plain hard to find these days, while the 6BL8 and 6U8 are plentiful.
You'll like the 222C. It is a very nice sounding amp. Oh, they will work fine with the modern EL84's.
 
Lifted from another thread

2. Replace the first resistor after the bias bridge, an 18Ω 1-Watt (brown-gray-black-silver) with a 33Ω 5-Watt resistor. You may have to adjust this value but it is almost always 33Ω. Reason; the silicon bridge is more efficient and the output voltage is higher than the selenium bridge.

This worked really well for me!

Dan
 
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In both the 222C's I have restored I have only done the 4x 20 ohm routine because it was most similar to the 18 ohm resistors that were already there (although I wish I had remembered to use 2 watters on the second amp instead of 1 watters which get almost too physically hot for comfort). With this method, at least the last time I checked, I had exactly 48 volts feeding the string of filaments of the 4x 12 volt pre-amp tubes.

Now proper bias voltage, on the other hand, MAY be a completely different story. I have been too lazy to check it properly. I know I have -18 to -19 volts on the EL84M's pin 2. But I know that is not a good indication of the current that the tube is actually pulling.

Since neither instrument has redplated its EL84M's and both sound very satisfactory I have been too lazy to perform proper current draw tests. Therefore, I wouldn't argue about anyone's choice of resistor line-up at this point.
 
I can't use metal polish right over the faceplate, can I?

I just tried a little bit now (with moderate pressure) over the volume knob area and accross the lettering (it's almost all gone anyways) and it doesn't seem to have done any harm to what's left...






I don't think the original's owner knew how to take care of his wifes... needs... there's scratches all around the headphone jack, as if someone hit the face with the plug, then dragged it over and into the hole-- a million times.
 
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Might try a magic-eraser on it first, then work your way up. I wasn't really sure what was on it, but since it's aluminum, it prolly ain't rust. Admittedly, I probly could have taken a better picture, but I opted to just keep it cheap. It'll sound as good as any once it's restored.
 
Might try a magic-eraser on it first, then work your way up. I wasn't really sure what was on it, but since it's aluminum, it prolly ain't rust. Admittedly, I probly could have taken a better picture, but I opted to just keep it cheap. It'll sound as good as any once it's restored.

Wow, well that shined it up right-quick! Good tip!

Also, ordered some K40Y-9 PIO caps, they should be here in a couple weeks!
 
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