tfm-35 diode identification ?

first, I am not that bright but am enjoying my experiences in learning how to do this and have not electrocuted myself yet....so excuse my not so intelligent questions when possible....
Picked up a TFM-35 today. Guy says(and I trust him), was working fine when it just sort of went poof. Opened it up, saw a couple of seriously fried diodes, sold it to me along with an oscilloscope. Just got it home, just opened up the case trying to identify the diodes. No problem finding them as they are seriously burnt and took out a couple of resistors with it. Could be bad diodes, could just be a symptom of something else (was not the cleanest inside, could even have shorted something out as at some time in it's life, the owner must have had a dog)
Anyway, I digress as usual. Knowing zilch about these, pulled up the manual to identify the diodes - I am new to this so usually have to first find it in the block diagrams before I know where to trace it in the circuit. Now I do have poor eyesight, but no way I can read the diagram of the TFM-35 - basically a jumbled blur of supposedly letters. Pulled up the TFM-25 manual and it is very legible, but obviously do not know if it is the same diodes.
So.....wonder if anyone could tell me what diodes and resistors these are - if you could just tell me the designation (D235, R273 etc)
The location - if you are looking at the Big diodes it has in there, on the TFM-25 they are listed as the 6a2f's, taking for granted the same on the 35, right above the area where there are only 2 of these, there are 2 resistors and 2 diodes I believe (is pretty charred, tough to tell from quick look) - anyone know what these are ?
On the TFM-25 they are R274, R273 and D233 and D235 - I can not tell what they are on the TFM-35 manual as it is so blurry.

Figured I would just replace these , stand back and see if that was the cause or the symptom before I do anything else.

Hopefully not too confusing - any help appreciated. I promise to learn to read the schematics better at some point so I do not need the parts location diagrams - did I mention I am not that bright ?
thanks for any info.

oh, on the TFM-25, they are the DS446 diodes. If that is the same as the TFM-35, would you also happen to know the equivalent diode used for the replacements, if any - thanks

Put your troubles behind you and send it off to Rita and let them send you back a "new" amp for ~$179 plus shipping. Even if your time is worth very little (to you), and with your eyesight, I'd say the "odds" of your "success" of fixing it by "hit/miss" are between slim and none. Probably more likely to just do more damage that will cost you more (and even if you "get lucky" you STILL won't have everything else tuned to factory specs, new caps, etc. - "like new"). Your business, but I'd bite the bullet, send it in and then have a great amp that you could enjoy for ~20 years!

while I agree that sending it to them would be the prudent thing to do, I must admit I do not always do the most prudent thing. I have been out of "real" audio for quite some time and have just recently got back into it. Buying older gear, it all needed some work, re-capping etc.
I have found that a big part of the hobby now for me is that I enjoy popping the hood and learning how all this works.
I once "restored" a 1977 Ford truck. I spent at least as much money if not more rebuilding the engine myself. Had never done that before so learned a lot (plus got some cool toys of course).
I just like getting my hands dirty and the self satisfaction when a plan all comes together.

now, I hope u do not take this the wrong way but has happened to me before. I am not quite sure why there is a repair forum when the answer is always to send it to Bob and Rita? I would imagine that there are others like me who are learning about this stuff and understand that we may make boat anchors along the way - but nothing ventured, nothing gained.
Again, i apologize if this comes across as rude, not meant to be, but I do feel it is a valid criticism. Since they have opened up their shop(which is great, do not get me wrong ) just seems there are a whole bunch of answers like send it off to rita.

Actually I emailed them last week wondering what would happen if i seriously screwed things up, and they were pretty much to the point that they will repair about anything for the $175.00 - with the extra costs of course as they have stated in their posts.
So I would think me replacing a couple of diodes and resistors would not do any more damage to this then it already has - so still $175.00.
I get even more practice replacing the caps, reading schematics etc - if I check out the unit every few caps and something still goes wrong - still the $175.00....
basically i lose the signature, which, now this is going to sound REAL stupid. Even if I did all of the work, replaced caps etc and it sounded like a million bucks, once it was decided that this would stay in the "stable" as a permanent amp(as permanent as they get around here anyway), there is a REALLY good chance i would still send it off to them just to get his signature on it - seems worth $175.00 to me just for his signature -
but ........ i am a stubborn guy and first want to see what i can do first just for the learning experience. hard to learn anything if I send it out to get repaired. One thing I have is time, may as well learn something

"repair forum" does not mean ANYONE can be shown how to repair ANYTHING. Common sense must apply and some folks are at a place where they can repair just about anything (Richp, BillD, e.g.); they just might need a little "sharing" of info to help them along. Very useful function of "repair forum". Others might be able to get enough help from such a forum to change a fuse or a binding post or avoid doing something stupid (like attempting a repair that is way over their head and cannot be "learned" via a "repair forum" setting but instead requires EXPERIENCE and TRAINING beyond that which could ever me garnered from a "repair forum". Guys here will let you know when they think you fit in the latter category. This too a valuable "repair forum" function!

Regards,
Ed

not to start a pissing contest and will be my last post on the subject.
Not knowing enough to find obsolete diodes falls into this category? I personally worked on every single guidance system for the minuteman missile that went down for repair. If it needed work, it did not go back online unless it had my signature on it, along with many others who worked there. I do not have the same equipment I was used to working with, but I am not too concerned with my soldering skills.
I am sure I would be totally lost if I sat down in front of the equipment i used to be one of the few people trained to use, but I am pretty sure I will be able to figure out an oscilloscope once I start using it. May take some pretty stupid questions along the way, but I am not too concerned about getting fairly proficient with it's use.
My schematic reading skills are as rusty as can be, plus ours were much different as what i worked on was pretty much just a mile of wire packed into a piece of equipment smaller then a basketball so all i really had to do to troubleshoot that was read thru dozens of pages of schematics following the route of the wires.......but again, I was pretty proficient at it as my yearly review and bonus can attest to.
But now I have too concern myself with caps and transistors , which a couple of months ago may as well have been wriitten in sumerian text.
But many have been very helpful and have pointed me in the right direction. I am only into this for a couple of months, but i am understanding more each day, am starting to understand the difference in the transistors, what does what etc.....which, without the help of others who have been so gracious in sharing their knowledge, I would probably still have no idea what they did.
So, what it comes down to now, is do i feel i am proficient enough to remove 2 diodes and 2 resistors and solder in the replacements ? I believe i can handle that. If not, bob and rita are always a mail truck away.
I have asked some absolutely stupid questions since i have been doing this, but the people on audiokarma have been bearing with me with nary a complaint. Actually, over there, they are the ones who got me started as I was looking for a repair shop and the vast majority of them told me if I am going to get into vintage audio, I need to learn to do alot of this myself - and then have answered my stupid questions without fail.

But now I ask for a replacement diode and I am told I am in over my head?
I am sorry my desire to repair this stuff, as part of my hobby, offends your sensibilities. in the meantime i will continue to look for a replacement diode and hopefully become more and more proficient each day, maybe some day even being able to answer a question for you. I will try not to burn my house down or electrocute myself in the process. i will just pretend it is a nuclear missile and maybe i will be ok.
Doubt if any are left, but hopefully they will not be test firing any old ones, hate to see my old handiwork go haywire as i was in over my head there too

It's not all about you . I was simply trying to explain the purpose of "our" repair forum (i.e., that sometimes it best to let a professional do the repairs - depending on the GENERAL circumstances)!
Knock yourself out!
Enjoy!

Hey Donberry, first welcome to the Forum.

Please think of it as a buffet & take what you like and ignore the rest.

Some of the more tech members will be chiming in soon I'm sure.

We always mention Bob & Rita because it is such a good deal.

Of course if you WANT to play around (and many do...it can be fun) go right ahead. The diode info will turn up soon.

FrankieD

donberry, I admire you wanting to expand your knowledge in this field of vintage audio. It all has to start somewhere, and we are not questioning your ability. I repair copiers and always run into problems that are new > a very challenging field to be in these days. I had one digital copier blowing a fuse on the power supply. One fuse out of 10! kept blowing after the copier cycled. Yes, had to get the schematics, trace the fuse back to find everything it ran, it was right there in print > toner motor being one of three item's this fuse ran. made sense, found the toner motor locked up. Why my little copier story? I too pull the cover off of my audio gear and think, I can do that > I am not in your situation currently but if I was, I would want to give it a shot myself. Try to find some readable schematics, that would help. Good luck.

Hi Donberry:

Welcome to the forum.

Can you upload a picture of the "disaster" area? I may have the Service Manual/Schematic.

Also, are the big power capacitors bulging at the top?

Rgds
Mayank

the big caps look ok, but i will swap them out anyway. As he said it was working until the diodes fried, i will probably see if I can't get it working 1st, then if i do will recap it - this way if i don't fix it, i will let Rita take care of that stuff.
I will try to get a pic up before i dig in, but going over the schematics(not thoroughly yet), I now believe the offending diodes to be D513 and D514, which are IN4004's, which would be great as those are so easy to get. I need to pop the top again though and examine it more closely as i thought there were 2 resistors fried there also (it really is a charred mess) so need to figure out what they are. Seems one should be R503, a 10K resistor, but not sure what the other one is until i get in and take a closer look...i am leaning towards R505, but that is a total guess until i get the meter out and trace it.
Is why for me, a legible parts diagram would be soooooo much easier. If I could just read the diagram in the service manual, no tracing or checking necessary, - get the parts, replace them and see if that was a symptom or the cause...(I am rooting for a diode just went out and that is the cause - a $2.00 fix would be awesome)
Wife is off work for the summer, so will have to actually get back to work on some other things, will get a pic up when i get back to it.
Thanks

donberry,

Nobody's trying to tell you you're in over your head; it's just good to get an idea of someone's level of expertise before you toss them off in the direction of playing with electrical stuff that can kill them. More than a couple of folks have showed up here asking questions with ZERO idea of what they're doing.

You've indicated your bonafides & I'm certain our resident experts will be able to assist you with your endeavor~ good luck!

I see that you've found a place where you can get some information

billd - I am truly grateful to the people who put up with my questions and like good audio, I enjoy the path of least resistance, after 29 years of marriage I get enough flak from the wife .
On a side note - I believe the problem is fixed, no smoke anyway. Turns out I have a broken output level so need to figure that out before I will know if I have any output.
Sure looks pretty all powered up now. Even got some component advice from Rita herself - great people. Actually I think a good xmas present will be Bob's signature on this.
Get the output figured out and I will be on to do the caps and adjustments

ok, I have to take the good with the bad - not totally giving up yet, but just replacing the resistors and diodes didn;t do it. Powers up now, but no output.
Checked a few things, seemed ok, so I just put it up for a bit.
Will pull it out and try it again after I get some other things done, but looks like there is a good chance I will be sending it off to Rita .
Will give it the old college try again before i do, hopefully learn a little more working on some other projects which will help me with this.
So looks as tho the "told ya so" had better go to the bull pen to warm up. It's not in the game yet, but may want to get it ready......
I still look at it as a learning experience - nothing ventured nothing gained.....