700B blew one Right channel 5A supply fuse

[62vauxhall]

Ya know what Gary, desolder that whole board in preparation for the new one, study the PL20 wire hookup diagram in the Archives.. After you get the board out ya need to check all board wires going to the backwall for shorts again. Can you borrow a Variac?

Even though it was becoming a point of contention, it does get tiring.

I'll take the board out and keep a PL20 hookup diagram on standby. In 25 words or less, what's the difference between it and a 14A from a benefit standpoint?

Once it's out, I'll look through those wires for shorts.

I was told a few weeks ago I might be able to acquire a variac. I'll pursue that and if successful, will get one this Sunday, even if it's a loaner. 10A, right?

I'll post again once I have it but may post sooner if I observe anything suspicious or blatantly obvious with the wires.

Also, before I forget, I asked about the sheilded cable coming from the volume pots. I think you said "start over". Were you meaning replace the cables as I proposed or continue to use the existing cable, cut the ends, and make new connections?

 

[62vauxhall]

After you take the board out could you take close up pics from the left to the right so I can look at some stuff??

I'll do that - front and back but not tonight. Probably tomorrow.

 

[laatsch55]

I would strip the old cable back.

10 amp variac, yes.

PL 20 is simpler, you'll see when you get it. More room, better traces and the bias tranny wires are soldered in at the bottom of the board with the rest of the wires.

If I had the board in my hands I could fix it, I'm just having a hard rime doing this long distance, but I'll get better at it. There is just sooooo much more that can be wrong...That's why I mentioned the variac, we can have problems ar startup , but with the variac and DBT in series we don't hurt any parts and we know at a lower voltage if something is wrong. That's a very nice board headed your way, the heatsinks on the 40412V's are still like new, would hate to see it a casualty from an existing prob;lem we haven't sniffed out yet...

 

[laatsch55]

I'll do that - front and back but not tonight. Probably tomorrow.

No problemm Gary. Going out of ton for 3 days starting Wed so i won't be back till Froday night...

 

[62vauxhall]

Before disconnecting the old 14A board, I wished to tag the questionably coloured wires to avoid mistakes when installing the new PL20 board. On looking at the diagram contained on the link you previously sent, there are two left channel wires identified as grey. From earlier posts, the wire attached to pad 9 should actually read blue. In my case, I did attach that correctly as it goes to Q11 base.

View attachment Phase Linear 700B 14A board connections.pdf

After disconnecting the 14A board, I took the requested photos. The jumpers were those I installed to compensate for destroyed trace holes. If a closer shot of a particular area will be helpful, let me know. My camera is getting ornery and become hard to turn on.

 

[laatsch55]

I was wanting pictures of the backwall....we are not going to rely on wire colors this time. It will be like " wire from 3rd pad from the right to the emitter of Q12" type of thing.

 

[62vauxhall]

My camera's giving me grief - it won't turn on and I'm trying to fix it. Even if I have to borrow a camera, I'll post those pictures before Sunday which is when I'm picking up a variac.

I got the board today. Very nice, and certainly in better condition than mine!

 

[laatsch55]

Sounds good Gary..

 

[62vauxhall]

Picked up a variac this afternoon. I asked for a 10A but they gave me a 7.5A. I think it was that or nothing, will it do? If not, I'll need to see about getting one somewhere else, just not sure where yet.

During the first test for shorts, I checked all the wires going to the board and got continuity on the Black ground wire, both Violet wires going to Q2 base and the center conductor of the co-ax lead going to the Right volume pot. The latter I know is not right.

I tested again but this time got no continuity from the Black or either Violet wires but still yes on that co-ax going to the volume pot.

Since the two readings did not agree, I thought maybe the batteries in the meter were getting low so I changed them and tested a third time. What I got then was exactly the same as the previous second test. Maybe, during the first test, two wires wound up touching each other or a ground?

I'll defer to your conclusion about that and re-test whatever you suggest.

Regarding the co-ax, I would personally feel more assured if I changed them. Which brings me back to that earlier question of whether the co-axial cable I have is good enough. I have about 20 feet of it so enough to replace all the co-ax leads or should I get something a more substantial.

Still using my own camera - if I press hard on the battery compartment lid it will work.

Attached are four pictures of the back wall (left top, left bottom, right top, right bottom) and a repeat of that co-ax cable I have here.

EDIT: Forgot to mention that those four diodes are still disconnected.

 

[laatsch55]

What 4 diodes?? That variac will do what we need to. If your shielded cable is multistrand conductor go ahead and use it....the continuity on the shielded bothers me, that HAS to get fixed...

 

[laatsch55]

Gary, that coax is not going to work. The insulation on the center conductor will not live in that hot environment...

 

[62vauxhall]

Diodes are D9 and D10 as per your previous post.

....Check D9,D10 on each channel again.

Please advise if I should re-attach them ASAP.

Tomorrow morning, I am going for some capacitors I need for one of my Innovative Audio garage sale finds and will get some suitable co-ax at the same time. Also going to pick up another camera I found on Craigslist but will be back early enough to replace the co-ax by the afternoon.

I'll post again once that's done.

Is there some specific designation or characteristic of co-ax that I should ask for?

 

[laatsch55]

If byour are talking about the diodes on the backwall, those are D14, D15. D9,D10 aare in the PL14 board...D14, D15 need to be on...

 

[laatsch55]

Diodes are D9 and D10 as per your previous post.

....Check D9,D10 on each channel again.

Please advise if I should re-attach them ASAP.

Tomorrow morning, I am going for some capacitors I need for one of my Innovative Audio garage sale finds and will get some suitable co-ax at the same time. Also going to pick up another camera I found on Craigslist but will be back early enough to replace the co-ax by the afternoon.

I'll post again once that's done.

Is there some specific designation or characteristic of co-ax that I should ask for?

You are looking for shielded with a CM designation. 2 conductor #22, or #20. Either one...

 

[62vauxhall]

You are looking for shielded with a CM designation. 2 conductor #22, or #20. Either one...

Yes, the diodes on the backwall. I'll re-solder them. Couldn't remember what their designation was and started looking through earlier posts. Should have gone back farther.

I'll get that cable (I hope) and post once it's on.

 

[laatsch55]

Sounds good Gary..

 

[laatsch55]

Gary, do you know what the Zoebel network is?

 

[62vauxhall]

No, I've seen the term but don't know what it is.

 

[laatsch55]

It's the .1ufcap seriesed with the 2 10 ohm resistors between the +/- speaker posts. They can cause a lot of problems if they are compromised...

 

[62vauxhall]

These? I can disconnect and check the resistors but don't think I check a capacitor with a DMM. Since I'm going to the parts store in the morning, should I get two .1MF capacitors - film type I presume?



EDIT. Just looked up 224 capacitor - says ceramic type. Should I get resistors too - 10 Watt?