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Help identifying tube part

Tinkerbelle said:
We all start somewhere. If you plan to get into tube amp repair, take it slow with simple steps. There are a few options to get you going.

Reading up a few restoration threads here will give some useful information. That article linked by maxhifi in post #15 above is very informative and has easy to follow details on simple capacitor identification and replacement. That type of article is recommended reading before diving in with a soldering iron. I would suggest spending quite a few moments digesting that information. Replacing old capacitors is often the biggest part of what is needed and certainly a good place to start. Also, rather than trying to address every potential issue in this console piece, just take a few simple steps to get familiar, while addressing the likely major culprits at the same time. Once you have some background knowledge sinking in you can start scoping out a plan for this unit. I would suggest identifying those caps we've indicated above. Take a look at the information on the side of each and write it down, such as 0.05µF (MFD), 200VDC, so you start to make a list of components that will need to be bought to replace them. The caps are usually relatively inexpensive. The expense associated with having a tech do the work is more likely the time expended. Once the needed cap values are identified you can move on to the replacement plan. Not everyone implements replacement the same way so you might get different valid input and opinions. Decide on a plan forward, purchase parts then replace is just one piece at a time and many here can assist with how best to approach this.

If you prefer a bit of personal help, an option would be to see if there are other AKers in your drive-able neighborhood who might be able & willing to share an hour or two with you to get started. Updating your personal information with your location so that it shows under your avatar lets others know where you are. Often, a helpful AKer is not too far away. In a similar vein, if you hadn't noticed, some areas have local meet ups, where AKers share music, equipment, ideas, and just good company. For example, this Events & Happenings forum has info on some that are currently ongoing. Lots of helpful folks attend these.

There are high voltages generated in tube equipment so read the safety guidelines to follow and stay alert. If you are unsure ask plenty of questions; don't guess or assume. Be safe and have fun with it.
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Invaluable advice. Thank you Tinkerbelle :)
I just finished reading the article maxhifi shared and I can’t believe what a great help that was in clarifying capacitors. Amazing. And I will be updating my profile indeed. AK’ers seem like a pleasant and extremely knowledgeable bunch!
 
angelaudio said:
Tremendously helpful, wow! Just finished reading the article and I am much more confident and knowledgeable. Thanks a bunch maxhifi, that’s a great article:beerchug:
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If you do a little more exploring on that website, there's a lot of material which is targeted at beginners and you may find interesting and useful. This is a good unit to begin with too, because it's simple, not very valuable, and nice and big so should be easy to work on. It's a good idea to practice soldering - there's no magic here though, just some basic skills to learn.
 
maxhifi said:
If you do a little more exploring on that website, there's a lot of material which is targeted at beginners and you may find interesting and useful. This is a good unit to begin with too, because it's simple, not very valuable, and nice and big so should be easy to work on. It's a good idea to practice soldering - there's no magic here though, just some basic skills to learn.
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I’ll definitely keep reading more on that site, there were even some articles linked within that article that I’ll be reading. I went in the garage to look at the amp with my new eyes and it is big but the circuit board seems rather crowded and some caps seem to be in such awkward and tight spots. Seems doable but definitely will require patience and a lot of pictures to remember how things are wired together because a lot of the terminals on the caps that need replacing are soldered to other terminals , 3-4 others in some cases.
 
angelaudio said:
I’ll definitely keep reading more on that site, there were even some articles linked within that article that I’ll be reading. I went in the garage to look at the amp with my new eyes and it is big but the circuit board seems rather crowded and some caps seem to be in such awkward and tight spots. Seems doable but definitely will require patience and a lot of pictures to remember how things are wired together because a lot of the terminals on the caps that need replacing are soldered to other terminals , 3-4 others in some cases.
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Here's an early 60s Japanese stereo receiver for comparison as an example of the sort of rat's nest which would make a poor first project.
onder2 (2).jpg
 
Tube safety is actually easy on an amp like yours - before a repair, unplug, test the B+ line off the rectifier, and when it's low enough, you can work. Or, get a 1k resistor and solder some wire clips to it (buy a bunch of those jumper clips things off of Amazon, clip one in half, solder the ends onto the resistor, insulate with heat shrink). Clip one end to the chassis, the other to the cap, wait a while (5 min). Then you'll be safe.

Realistically, the B+ line will bleed down pretty fast anyway, and you can always measure the work area with a meter before hand. It's not like a TV where you have weird voltages in weird places.

The workflow is easy - replace all paper/wax and electrolytic caps, test, then fix any additional trouble areas. The Sams will have voltage/resistance guides for every tube socket.

Also, the voltages aren 't exact - if it says 150 and you've got 140 or 160, you're probably good. If you have 180 or 100, there might be an issue.

Voltages - the cathode is less than the plate in audio. The grid is less than the cathode, but pretty close. The screen grid (2nd grid) is close to the plate. The third grid is often grounded. THe schematic wil list the voltages referenced to ground (the chassis, usually), and note any exceptions.

Don't be surprised if a resistor or two is bad in there, too. Go slow and steady, and you'll get there. Be neat, make sure you suck up any 'nuggets' of solder or such (they cause random issues and are no fun).

Start at the power supply, then the output sections, audio stages, and work back. Note the power supply isn't regulated - it'll be wrong until every other stage is fixed and working right.
 
Please be sure to understand what the markings on the caps mean and which markings determine the positive or negative side of a cap so that you put them in with right polarity and don't blow them up after they are in the wrong way.
Also understand the ratings on them in regard to maximum applicable voltage. General word, higher in voltage rating is alway good, never go lower.
Look for film or sometimes 'poly' caps for anything that is in the signal path way. They are more stable and have less distortion so it will sound better. Electrolytic a for the power supply are ok but they have the polaritie requirement.
For the beginning take pictures of the ones you want to work on to remember which way was what.
 
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