New (to me) amps

[quindecima]

I have been looking for amps for my system and finally found a couple, they arrived today. they are Adcom 555II's. They arrived well packaged and the condition is way above usual. I am going to do some mods on these. First thing I did was fire them up and check the MV across the speaker terminals. They are fine and were dead quiet when I fired them up. I am going to do all stages and the first is the PS. I will post as things progress. :bouncy:

[quindecima]

So far so good. I had to look hard to find 4 caps in the PS but I finally found them under the plate that holds the bridge rectifier and bleeders on. It's the only place they could be after looking at it. They were 100nf at 100v and I replaced them with 100nf at 250V I'm waiting for some X2 caps for the AC line and the new bleeders and that part will be pretty much done. I'm going to change the bridge from 25amp at 400v to 50 amp at 600v, Bleeders from 3.9Kohm at 3 watt to 4.7Kohm at 7 watt overkill but they were available. I'm going to filter the AC side of the bridge with a 10nf at 400v X2 cap. Not present now.

[Wagner]

What's (as in function) 100nF (.1uF)?

[quindecima]

Yes

[Wagner]

Yes
What is their function?
I am asking as I thought I understood you to mean re-capping/rebuilding when you wrote "I am going to do all stages and the first is the PS"

What are the values of the big cans?

Nice amps, you get them for a good price?

I have plenty of .01uF X1/Y2 caps if you need a few (rather than pay shipping on an order so small)

Thomas

[quindecima]

They are bypassing caps.

The big cans are 100v at 15000uf

I would be better off with the X2 caps their voltage rating is less than 2500v while the X1 is 2500v and below 4000v but.........are they long lead? Whats the voltage?

I got them for a good price, condition is everything on these. about 100 to 150 less than they go for on Epay.

[Wagner]

I would be better off with the X2 caps...............
I don't understand but that's "OK"

I'll post the specs on the ones I have in a few, I have two lead types as well, one dressed short for PC board work and the other batch with longer leads

[Wagner]

Here's the types I have. The listings have a link to the data sheets for each device. The TDKs have short kinked leads which I just straighten out and use where they'll work. Don't know why a device with leads like this was sold loose (a little on the short side, I missed it when I ordered them, I believed the "pic"):
http://www.mouser.com/Search/ProductDetail.aspx?R=CS17-F2GA103MYNSvirtualkey52130000virtualkey810-CS17-F2GA103MY

http://www.mouser.com/Search/ProductDetail.aspx?R=DE2F3KH103MA3Bvirtualkey64800 000virtualkey81-DE2F3KH103M

[quindecima]

Thomas,

The voltage is too low and they are ceramic, not what I am looking for but thanks you for the offer.

[Wagner]

Thomas,

The voltage is too low and they are ceramic, not what I am looking for but thanks you for the offer.
Too low? They are X1/Y2 impulse rated (that's a 4000V and 5000V respectively) 2600V for the TDKs

What are you using these for?

I don't think you're going to find any X1/Y2 Class Certified products in anything but ceramic:
http://www.mouser.com/pdfdocs/Safety.pdf

I really am curious though, just exactly where are these going in the circuit (what are they doing)

[quindecima]

That's the pulse rating not the steady voltage. The steady V on those is 275V I would like at least 380V. The purpose is to filter the HF noise on AC. I have found them in mica but it is the long leads that are the problem

[Wagner]

That's the pulse rating not the steady voltage. The steady V on those is 275V I would like at least 380V. The purpose is to filter the HF noise on AC. I have found them in mica but it is the long leads that are the problem
The TDKs are rated @ 400VAC

What is the lead length you need? These caps are the types used by builders for line noise suppression/filtering, ie: radios/receivers, have worked well for me

Good luck, hope you find what you need

Thomas

[quindecima]

Ceramic caps act like a microphone amplifying AC noise that's why I would rather use Film.

[quindecima]

O.K. here's the current situation. The caps are going across the secondary of the main transformer so I don't need X2 caps there, a short there would not be as catastrophic as one across the mains. I will put a new one across the mains because the one there now is ceramic and I don't need the long leads.

I finished the PS stuff this morning and fired the amp up. I will do this after I work on each stage so if I screw up I will know where I did it. It's sitting here now dead quiet.

[quindecima]

Here we are today. The X2 caps I tried to get with the long leads actually came with them, not as described at all. I replaced the little caps you see that are 47uf at 160V with 120uf at 200V and bypassed them with 22uf at 600V orange drops. I also replaced the Ceramic bypass cap on the mains with one of the X2 caps. I am debating if I need to get to the bottom of those 4 boards to replace the 68pf at 500V film that are there with the same thing.

Addendum. I replaced the film that were there with Micas.

[quindecima]

I have moved on to the input board. This was going to be the most challenging but I looked at it and thought that if I was real careful I could work on it without removing the board. Hah, fat chance, there is no way I can remove some of those itty bitty parts without having the board mounted in a board holder. I replaced one trimmer but that is as far as I am going until the board holder gets here. I am going to have to number all the wires ( they are marked on the board) it doesn't look too bad mostly labor intensive.

[quindecima]

I managed to mount the input board on my bench today in a pretty secure manner and changed out 8 diodes to a higher value. The darn things are the size of a large ant, I had to break out my magnifying glass on a lamp that I use for tying flies so I could see the things. I back lit the board so everything stood out pretty well.

[Wagner]

Here we are today. The X2 caps I tried to get with the long leads actually came with them, not as described at all. I replaced the little caps you see that are 47uf at 160V with 120uf at 200V and bypassed them with 22uf at 600V orange drops. I also replaced the Ceramic bypass cap on the mains with one of the X2 caps. I am debating if I need to get to the bottom of those 4 boards to replace the 68pf at 500V film that are there with the same thing.

Addendum. I replaced the film that were there with Micas.
I really wish I understood what this deal/problem is you've got going with the caps' lead length?
I also have no clue what it is you are up to, but I hope whatever it is it all works out to your satisfaction! :yes:

I assume you are changing out all of the amp's electrolytics, yes?

Enjoy!
Thomas

[quindecima]

Yes, almost all electrolytics and other caps. the lead length was a problem on the bridge rectifier, I had to run a cap across the AC and the short leads on most caps wouldn't reach. It is not a problem anymore I resolved it forthwith. These amps have a known problem with a bunch of bad caps the manufacturer got from a supplier, they leak land screw up the boards and its a big job to clean them up afterwards. Lucky for me the two amps that I got don't have the caps leaking and I am making sure they are replaced before they do. I am also making a few other upgrades while I am into it.

[quindecima]

Still waiting for the rest of the stuff from Mouser but today a little package from China. I'm going to install a speaker protection board to protect the speakers and they make these little boards over there you just have to assemble them, takes about 1/2 hour at a slow pace. Each board fits in the bottom of the amp and controls two speakers.

[quindecima]

The last of my components arrived and I have upgraded the output terminals and the board is completed. Now to reassemble and fire it up.

[quindecima]

I had to replace 4 of the diodes I installed. I could tell the cathode end on the new ones I installed but the ones from Adcom were colored with a different band and I had a hard time discerning them. My right output boards have some bad output transistors so it looks like they are going to be replaced.

[quindecima]

Here is the final story, I dropped some solder down on the board and it fell between the collectors and bases on the left side (nice) and then I had a bad trace on the right that blew a couple on the right so I had to replace all of the output transistors there. I took the output board out so many times trying to figure out what was the problem that I screwed it up a little but it is in fine shape now due to some outside help I am a happy camper. If any of you have Adcom Amps and want some info give me a shout and I will steer you in the correct direction.

[Challenger604]

Hi Larry!
Seems you had a lot of fun!!
C

[quindecima]

Yes, I started on my other amp and it's turning out much nicer. I have the correct length caps and am doing it a little different as far as disassembling it. It will be a much cleaner job, won't work any different but cosmetically will be better.

[quindecima]

I'm done this is it.

[Challenger604]

I'm done this is it.


Is it working?? LOL!!
Nice!!
Pretty much a brand new amp!
Congrats!
C

[quindecima]

Oh yeah, it's working very nice. I ran it today at idle and it is dead quiet and less than 1mv at the speaker outputs. I learned a lot on this that I passed on to my other one. One thing left is I am going to replace the power cord with an IEC plug with a filter on it. I am waiting for a square chassis punch, I couldn't figure out how to do it without making a mess without the punch.

[quindecima]

Well, the chassis punch came today and I jumped right on it. Last time I am doing that!!!! 18ga steel probably a little much for it. I turned the nut as far as I could muster up the strength, even lubed it, then I took it out and cut it out with a small cutting wheel heck of a lot faster. Actually a PITA for what little I gained. The best way to do it is to unsolder the outputs and inputs and remove the panel, I need a small libation.

[Krunchy]

Here is the final story, I dropped some solder down on the board and it fell between the collectors and bases on the left side (nice) and then I had a bad trace on the right that blew a couple on the right so I had to replace all of the output transistors there. I took the output board out so many times trying to figure out what was the problem that I screwed it up a little but it is in fine shape now due to some outside help I am a happy camper. If any of you have Adcom Amps and want some info give me a shout and I will steer you in the correct direction.

Thank you sir, I'm gonna take you up on that offer, I have a GFA5802 that is not working, hopefully it is something that is obvious or stands out, I have not had a chance to look into it yet but will do so as I get a chance.

[quindecima]

Describe the problems it exhibits as completely as you can.

[Krunchy]

Describe the problems it exhibits as completely as you can.

While pushing it a at lively level it suddenly stopped working, while simultaneously bellowing out an obvious wisp of smoke, that's when (through my acute powers of perception) I knew it was serious :D
I promptly shut off power and awaited instantaneous combustion, luckily it did not manifest. I'll take the top off & have a peek to see if anything stands out as the likely culprit.