A Tube Amp Restoration Walk Through

[Zeshin]

You doing something like that would not surprise me a bit Please tell you strip the chassis first... or do you leave water saturated abused caps and resistors in place?

I'm sorry but can't be positive about something I do not agree with. You might think being hypocritical is okay but I don't. I have no issue with the cleaning I just think the chassis should be stripped first and the amp given a proper rebuilding after the cleaning. I think the cleaning is awesome.

IMHO the entire problem with doing this right is the cost....high labor and low profit.

I've been following this same thread over on the Klipsch community forums, which has unfortunately now been locked down, and I must say that you took a rather different tone over there regarding ultrasonic cleaning:

https://community.klipsch.com/index...tage-tube-amp-restoration-walk-through/page-3

Glad to hear you have come around though, as I also think the ultrasonic cleaning is awesome.

 

[AEA Audio]

You doing something like that would not surprise me a bit Please tell you strip the chassis first... or do you leave water saturated abused caps and resistors in place?

I'm sorry but can't be positive about something I do not agree with. You might think being hypocritical is okay but I don't. I have no issue with the cleaning I just think the chassis should be stripped first and the amp given a proper rebuilding after the cleaning. I think the cleaning is awesome.

IMHO the entire problem with doing this right is the cost....high labor and low profit.

There is actually no need to strip any components out of the chassis, except for the transformers.

Many people are concerned about possible damage to resistors and capacitors when they first look into this type of cleaning. But they find that these components are not harmed. Electronics manufacturers and restoration experts have been using water washing, and even ultrasonic cleaning for many years. Electronic components actually emerge with lower humidity content than before they were cleaned and then dried with these methods.

Any water that might seep into components is evaporated in the drying process. Drying should be done directly after cleaning. This type of low-temperature long-duration drying process is very effective. In fact, there are many well documented cases of tube equipment being completely restored using this technique even after being submerged for days and even weeks from flooding. Even units submerged in salt water can be restored by soaking them in freshwater for up to weeks, with the water being changed regularly to dilute out the salt. Once the unit is thoroughly dried, there is often no residual damage from the water even in these extreme cases. In the case of ultrasonic cleaning they are only wet for a few minutes.

You might wonder why this is. In the case of carbon composition resistors, they are made of a mixture of powdered carbon and a ceramic material, encased in molded Phenolic resin. These materials are highly impervious to water or water damage. Carbon comp resistors will change value over time when stressed with over-voltages and overheating, but not by absorbing water. The only negative effects excessive water absorption has on them is if they are exposed to very high temperatures, such as soldering or overheating from over-voltages caused by things like tube failure or failed capacitors. Moisture absorption is not a cause of failure under normal operating conditions, even in hot running tube amps. Likewise, ceramic disk capacitors also are not a problem because they are made of water resistant materials, even though they can be affected by water absorption with high voltages applied. In both cases this lack of any harm is because there is no internal moisture content left after proper drying.

 

[jaymanaa]

Exactly my thoughts on the subject, but I usually change all the resistors anyway, just because they are so much quieter now, and very affordable even for 1 or 2 %ers. The only amps I usually leave the resistors in are Allens (they used IRCs), and Fishers as they seem to have a big effect on the tone that the Fisher crowd likes. I like metal film for my own gear. I never leave ceramics either, I just don't feel they have a place in audio. maybe some NPOs in a very limited number of manufacturers, but that's it. I prefer silvered micah for the tiny stuff and an assortment of films and oils for other spots. I've been using an ultra sonic tooth brush for years, and it works very well for that, so why not I figure. My one huge pet peeve is techs that claim rebuilds and the RCAs are still filthy and oxidized. You can see that on 1000 dollar Scott integrateds from maple leaf, etc...... Really now, how long does it take to polish RCA connectors? On the subject of using old resistors, who made those nice looking red ones for Fisher?

There is actually no need to strip any components out of the chassis, except for the transformers.

Many people are concerned about possible damage to resistors and capacitors when they first look into this type of cleaning. But they find that these components are not harmed. Electronics manufacturers and restoration experts have been using water washing, and even ultrasonic cleaning for many years. Electronic components actually emerge with lower humidity content than before they were cleaned and then dried with these methods. Water is the worlds universal solvent, yet a lot of folks are scared of it, and rightfully so if not done properly I guess.

Any water that might seep into components is evaporated in the drying process. Drying should be done directly after cleaning. This type of low-temperature long-duration drying process is very effective. In fact, there are many well documented cases of tube equipment being completely restored using this technique even after being submerged for days and even weeks from flooding. Even units submerged in salt water can be restored by soaking them in freshwater for up to weeks, with the water being changed regularly to dilute out the salt. Once the unit is thoroughly dried, there is often no residual damage from the water even in these extreme cases. In the case of ultrasonic cleaning they are only wet for a few minutes.

You might wonder why this is. In the case of carbon composition resistors, they are made of a mixture of powdered carbon and a ceramic material, encased in molded Phenolic resin. These materials are highly impervious to water or water damage. Carbon comp resistors will change value over time when stressed with over-voltages and overheating, but not by absorbing water. The only negative effects excessive water absorption has on them is if they are exposed to very high temperatures, such as soldering or overheating from over-voltages caused by things like tube failure or failed capacitors. Moisture absorption is not a cause of failure under normal operating conditions, even in hot running tube amps. Likewise, ceramic disk capacitors also are not a problem because they are made of water resistant materials, even though they can be affected by water absorption with high voltages applied. In both cases this lack of any harm is because there is no internal moisture content left after proper drying.

 

[Pio1980]

Anyone know how Tektronix cleaned for a refurb?

Sent from my SM-N900V using Tapatalk

 

[tcdriver]

Thank you so much for posting your cleaning and restoration process. The detailed description of your process and pictures are very helpful. I do have a question about the power supply capacitors you added. It looks like, as best I can tell from your picture, that you added capacitance in parallel to the existing capacitors. Is that correct or did you disconnect the originals? If you did parallel the new and old, did you check the original capacitors for leakage? Thanks again for the excellent write-up.

 

[Mystic]

We are located in San Mateo.

Which could explain the typo "silicon" -- you're in the SV and that spelling is likely burned into your heads and (typing) hands.

 

[buglegirl]

Hiya,

Which could explain the typo "silicon" -- you're in the SV and that spelling is likely burned into your heads and (typing) hands.

You rabble rouser!! That word is sacrilege here in the tube forum.

Thirty lashes with a wet noodle for you and 1000 hail Amperex Tubes.

I was so hoping we never get to the third utterance but now the tube forum needs a Sage cleansing.

Thanks A Lot!!

Frannie

 

[Pio1980]

I remember gear being sonic dipped whole in freon baths before refurb. I think many OEM aftermarket support shops did this for everything from military commo and other stuff to typewriters, and Tek may have used this method.

Sent from my SM-N900V using Tapatalk

 

[buglegirl]

Hiya,

I remember gear being sonic dipped whole in freon baths before refurb. I think many OEM aftermarket support shops did this for everything from military commo and other stuff to typewriters, and Tek may have used this method.

Well to be fair when I was using this all the way back in the 80's the equipment was a bit newer than these 50 year old amplifiers.

Heck if anyone wants a summer science project do this.

1. Buy a smaller ultra sonic cleaner.

2. Take out some old components from some vintage piece of audio gear.

3. Carefully test said components and document all results using rigorous testing parameters.

4. Put components into cleaner and let em go for a typical cleaning cycle.

5. Take out components and test them again after the prescribed drying cycle.

6. Repeat 3 to 5 using brand new control group components.

7. Put aside both groups of components and let sit for a year or two.

8. Come back in the summer of 2017 and let us know your results.

Frannie

 

[Westy56]

I think the hardest part for a first timer, is getting the right parts together.

That's it in a nutshell for me. :yes:
When I find the parts, I've had no problem unsoldering and replacing.

 

[jaymanaa]

That's it in a nutshell for me. :yes:
When I find the parts, I've had no problem unsoldering and replacing.

That's my main reason for wanting an accurate schematic so I can make one parts order and have everything. If I'm doing a Stromberg 433, I already know that it's getting every single resistor and cap replaced. I've been doing it long enough now that I have a pretty good parts stock. Still, every now and then I'll find something odd that I have to order, so I'll order 6. I can understand some guys that don't want to mess with it, and would rather just send it off, but I do contend that anyone with an average IQ can rebuild a tube amp, especially with the net and AK at their disposal.

 

[Westy56]

You know Jay, you would make a very good parts package dealer for vintage restorations.
I know that some people already do it, but I haven't found one I was happy with.

 

[jaymanaa]

You know Jay, you would make a very good parts package dealer for vintage restorations.
I know that some people already do it, but I haven't found one I was happy with.

That's not a bad idea, I'm actually pretty good at getting the stuff together and matching everything. I even heat the resistors before I match them if I have a spot where I want a carbon comp Allen Bradly. I've thought about putting together a kit or two as well. If everything goes as planned, I retire next March, so I'm going to finally have some time on my hands. heck, now I get up at 6 to be in at 8, then get home around 5, filthy dirty. So by the time I shower up and grab something to eat, it's too late to really do much, except for maybe some light house work to help the wife who works more hours than I do. I can't wait for retirement, and can't understand these guys that say they have nothing to do. I just don't get it, but I do feel bad for them, my Union forces them out at 65.

 

[NOSValves]

I think the red resistors are German film type, probably Roederstein or Rosenthal. I see a lot of them in vintage German gear and some vintage American Hi Fi in critical apps.

Sent from my SM-N900V using Tapatalk

I seem to recall tearing them apart and finding that they are indeed carbon just built completely different than what we are all used too...

 

[BuzzK]

I got so caught up with the flotsam and jetsam, I forgot to thank the original poster for sharing his beautiful restoration job on the Fisher. Very, very nice -- thanks for taking the time and effort to share it on AK.

 

[bobabode]

Nice write up and welcome to AudioKarma, AEA. It's always a pleasure to see a contributing vendor share your hard won tips and tricks of the trade with us hobbyists. Thanks :yes:

Cool company history you have on your website. :thmbsp:

 

[perchdog]

It would be interesting to see photos of an amp in far worse shape going through the process. Minor rust, caked with cadmium powder etc. What if any improvements are to be had in switches and etc. My Fisher 400 sat in a basement a long time before I got a hold of it. The switching and controls were a challenge to say the least

 

[Steve O]

Originally Posted by Pio1980
I think the red resistors are German film type, probably Roederstein or Rosenthal. I see a lot of them in vintage German gear and some vintage American Hi Fi in critical apps.

Sent from my SM-N900V using Tapatalk

I seem to recall tearing them apart and finding that they are indeed carbon just built completely different than what we are all used too...

Just for the record, those red resistors found in a lot of the later Fisher equipment and imported German gear are generally considered to be Beyschlag carbon film types. IME, they're quite stable over time, sound pretty darn good and require replacing very rarely...usually the result of catastrophic failure elsewhere in the circuit.

 

[Negotiableterms]

Great cleanup job, Tink! Above and beyond the call.

AEA, welcome to AK!

 

[AEA Audio]

Great cleanup job, Tink! Above and beyond the call.

AEA, welcome to AK!

Thanks for the warm welcome all! We are very happy to be here on AK and share our knowledge with the community.

We will get back to responding to questions concerning our restoration process tomorrow. Please keep all your questions, concerns, and friendly criticism coming.