SPEC 2 Filter Cap Purchase Source

[slipstream55]

Anyone have any experience with the wire gauges used in this amp. I have wire-wrapping experience and may have to replace a few wires but I'm wondering why solder wouldn't work as well or better than the original wire-wrap attachment method?

And is solid conductor better than stranded wire?

Comments are welcome.

 

[EchoWars]

Solid conductor makes for a smaller wire within the same gauge. But it's fragile.

A lot of the internal wire in the Spec 2 is 20 and 22ga solid. I went to shop for a wirepwrap tool that large a few years ago and shied away after seeing $60+ prices. That, and to have enough wire to re-wrap a busted wire you have to replace the wire altogether. Plus, wirewrap wire that large is expensive and damned hard to find (can't use just any solid core wire, as it will fracture too easily).

 

[slipstream55]

Echo: I hear you on the wire-wrap tool prices. I should have completed this restore while I still worked at Boeing and had the tools available.

So...then there would be nothing wrong electrically/sonically with using either solid or stranded wire and soldering other than I am straying from keeping this SPEC 2 as close to original as can be. I think I've kinda shot the "original" condition thing down with the repainting it is going to need and some of the things I am replacing inside the box.

Pacific Stereo PMed me and said the materials he used for the "spatter" effect paint are no longer available. In recent years, I've seen a lot of equipment cabinets come into our lab that had this same "spatter" effect paint on the side panels that was a perfect match to the SPEC 2 covers. I wonder where these cabinet vendors are getting their painting done?

 

[slipstream55]

EchoWars or markthefixer:

Will the high-lighted subs work for the stock transistors listed below:

2SC1384 (Q12, Q14, G15, Meter Board) - Mouser 512-KSC2690AYSTU (or AYS), in stock
2SC945 (Q13, Meter Board) - Mouser 512-KSC1845FTA, in stock
2SB507 (Q17) - Mouser 863-MJE15031G, in stock

Thanks.

 

[slipstream55]

Can anyone verify for me that Mouser part 512-KSD1616AGBU will sub for a 2SC1384 (which is unavailable). I found a thread on AK that showed a 512-KSD1616LBU would sub but it is now obsolete. The 512-KSD1616AGBU is not obsolete and it is in stock.

Thanks.

 

[Blue Shadow]

The beef with tantalum are that (1) the early tantalum caps from the 70's and 80's were not terribly reliable, (2), in the audio path, they simply do not sound good, and (3), they do NOT take overvoltages or reverse voltages well, whereas an aluminum electro can tolerate reasonable overvoltages pretty easily. So for the last few years I've not automatically been replacing tantalum caps with aluminum or film, unless the cap is in a position where overvoltage is possible or where the cap is carrying an audio signal. I may (and often do) simply replace the old tantalum with a new one with the voltage stepped up to the next tier.

Finally some common sense when it comes to Tants. I've had a failure in a piece of test gear but in some audio equipment I replaced wet tants, they have to go, they are like 'lytics being wet and having similar old age issues, with new regular tants.

I believe the wholesale replacement with 'lytics due to your first and third reasons are because many doing recaps can't tell if a cap is in the audio path and 'lytics are cheaper.

Thanks for your comments on this issue.

I have been asked why I wanted to replace the relays. These may be functional but they look like crap.

View attachment 872187

These may look horrible and still work but there are for sure some scars on the contacts and replacing them is a step always taken on bigger amps to avoid having to go back in.

Fun watching this move forward.

 

[slipstream55]

Regarding "specs" on transistor data sheets (of which I am trying to learn how to read/understand)...so long as the spec of the sub part meets or exceeds (generally) the spec of the original part, that sub part can be used as a replacement for the original part if the original part is no longer available?

 

[rcs16]

2SC945 (Q13, Meter Board) - Mouser 512-KSC1845FTA, in stock

Use the proper part if available, and they are, so use ksc945c

2SC1384 (which is unavailable)

2sc1384 is obsolete, so use a KSC2383 or a KSC2316. 512-KSC2690AYSTU will also work but the holes may need enlarging.

Regarding "specs" on transistor data sheets (of which I am trying to learn how to read/understand)...so long as the spec of the sub part meets or exceeds (generally) the spec of the original part, that sub part can be used as a replacement for the original part if the original part is no longer available?

Generally speaking YES, form, fit, function.

 

[slipstream55]

I have identified 863-MJE15031G as a suitable sub for the 2SB507 (Q17) transistor on the Meter board. I looked at the MOSPEC data sheet for a 2SB507 and the specs are better on the 15031 part but very close. Could someone be my second set of eyes and verify this as a blessed part? Thanks.

Mark

 

[slipstream55]

Use the proper part if available, and they are, so use ksc945c

512-KSC945CGBU?

 

[slipstream55]

Restoration Update:

Here are some "before" pictures of the Left Amp board:

Apparently, someone got creative with the relay and STV3/STV4 diode packs.









Back of the board doesn't look too bad.



The output transistor sockets should clean up nicely.



More creative hacking:

 

[slipstream55]

Acquired this recently.

This solves my Speaker Protection relay quandary:

 

[slipstream55]

One more update "before" picture of the Left Amp board:

It surprises me that as bad a shape as the amp is in, these connector posts are pretty clean compared to other boards I have seen. A little light cleaning anyway.

 

[slipstream55]

Friday night fun (Camera's having a hard time focusing tonight):

Left Amp board connector pins cleaned up very well with MASS metal cleaner and minimal elbow grease. I use this on the tarnished RCA jacks for many of the vintage components in my collection. This stuff is awesome.

Before:



After:



Available at your local Ace Hardware.

 

[slipstream55]

Drat. No stock on the KSA733CLTA (Q11). Does anyone know if the KSA733GBU will work instead?

Thanks.

 

[OverLoad]

Drat. No stock on the KSA733CLTA (Q11). Does anyone know if the KSA733GBU will work instead?

Thanks.

Yes, they are the same parts aside from transistor pinouts and the less important in this case, hFE ranking. . KSA733GBU will be EBC and KSA733CLTA ECB pinout. The pinout poses no problem since the transistor layout on the board is in a triangle pattern. Having said that, Digikey and Mouser have thousands of the center pin collector version in stock. You don't need the "L" hFE rank so purchase KSA733CGBU (ECB pinout).

 

[slipstream55]

Thank you, OverLoad.

I found the hFE table looking at the Fairchild and then, the On Semiconductor data sheets before realizing the classification types in the table correlated to the "L" in the KSA733CLTA part number. That's when I saw the hFE difference between the two parts. I wasn't sure if the hFE difference was important in this application (SPEC 2 use).

 

[slipstream55]

Another update (not good):

I am seriously beginning to wonder if this SPEC 2 wasn't used as a boat anchor at some point in its life. It was bought in Norfolk, VA after all.

I did a visual inspection of both Amp boards. I don't know if it was EW or markthefixer that said the wire wrap wires were very fragile. I think I would use stronger words to describe their condition. Between the two boards, I have found 3 broken wires, 2 cold solder joints and 3 loose wires going to the output transistors.

I am no longer a proponent of wire wrap technology that is 40 years old. I am not saying I want to do a wholesale wire change but the broken and crap connections are going to get new wire and properly soldered assuming the wire wrap pins will take solder. Also found a broken STV3H diode pack. Luckily, I bought a bunch back in 2008 when I was first collecting parts for this project. Take a look at the pictures below:

Left Amp board broken yellow wire and cold solder joints.



Not quite sure what to call this. Shoot the piano player (would be repair tech in this case).





The years and living conditions were not kind here.



I'm glad this wasn't an STV4H diode pack. I do have two of each flavor on hand, though, just in case.

 

[slipstream55]

Couldn't find any KSA992FBU transistors in Mouser stock so I ordered some KSA992FATA parts. I hope these will work. This is for Q3-Q6 on the Meter board.

(Well, stupid me. I found and ordered the KSA992FBU transistors thru Digikey. I would still like to know if the KSA992FATA would work as I now seem to be building up a parts repository).

 

[redk9258]

The only difference us bulk vs. tape packaging.