Repair question re: threshold 400a

Jump to Latest
#341
barchetta said:



I can tell you all of the joints had a nice "creep" affect where the solder would look as if it was creeping up the wire.. thats why I dont get where I went wrong.. but who knows.. maybe I missed one..
Click to expand...


I'm not sure, even in context, whether this was of concern to you or not, but I thought I would toss in that this is called wetting and is good.
All the textbooks say that a solder joint should be shiny, but some of the newer solder formulations do tend to have a disconcerting matte finish when they cool.

Grey
 
#343
when de-soldering parts from circuit boards watch for the unintentional
splatter. I did a quick repair on one of my amps one day, put it all back
together, fired it up... and toasted a few resistors! I could not for the
life of me figured what i had done wrong. Then on running an eye
over all the traces, i saw where a flick of solder had made a bridge
between two traces.

(also a good reason to always wear eye safety gear when soldering)
 
#344
moe29 said:
when de-soldering parts from circuit boards watch for the unintentional
splatter. I did a quick repair on one of my amps one day, put it all back
together, fired it up... and toasted a few resistors! I could not for the
life of me figured what i had done wrong. Then on running an eye
over all the traces, i saw where a flick of solder had made a bridge
between two traces.

(also a good reason to always wear eye safety gear when soldering)
Click to expand...


Grey: Thanks.. makes me feel much better cuz my solder has a matte finish.. I hate it next to the shiny factory stuff.

moe29: Yeah; I know what you mean.. and I may have missed some spatter.. about to find out.. iron is heating up now..

Radio Shacks multi-temp iron sux.. they dont even carry tips.. forget it.. I'll order on on line. If I am gonna spend that kinda money I am buying a bunch of tips for it!

Sorry this is getting off subject.. I'll let you know when I reinstall and smoke test it..
j
EDIT: and they dont even carry flux! RS ain't what it used to be thats for sure.. They do carry huge brass fuse holders for your "thumpin" car stereo.. yeeesh.
 
#345
Hi Joe,
The dull finish on some new solders takes some getting use to for us "old" guys. 😉

One reason I clean a board every time I work on it is to avoid solder bridges or splashes. Clean, then inspect every single time. Not every joint, just every job.

There are some temperature controlled stations for about $100 CDN or less. I love these as I buried several Weller WTCPN (or whatever they were) and equiv. stations. I like the ones with the digital temp. display. I even took mine apart and calibrated it. Tips last a long, long time on these.

I'm very happy you didn't use that corrosive flux. MG chemicals makes some. It is not expensive.

-Chris
 
#347
Joe,

If I may jump in here, earlier in the thread I posted recommendations on soldering stations. I'd go that direction if I were you.

Regarding the solder, dump the 4% stuff. Either buy the Cardas stuff I sent in a previous post, or go back to radio shack and buy a roll of their "normal" solder. Their standard solder is good stuff.

As an alternate, if you have a real electronics store near your house, go there and buy a weller iron (also lowes or home depot), regular electronics solder (small diameter) and ELECTRONIC flux. You will also want a can of flux remover...

Good luck,

Steve
 
#348
Thanks guys.. I picked up some "normal" solder.. and I will look at the stations you recomended Steve.. I guess I didnt anticipate "rework" or I would have bought one earlier.. besides I am eyeing up a project amplifier.. hehehe.. you guys are gonna get tired of all my questions.. I am trying to google as much as I can though.. My intial inspection of the board is scary because my work looks good.. but I will heat each one up and mark it with a marker so I miss none..


My girlfriend is not getting a little irritated with me.. but thats okay.. there are many fish in the sea. 🙂


EDIT: Steve or anyone, can you make any suggestions on a reasonable scope for someone starting out? I have been told I want 300khz.. but boy that pricey.
 
#349
Hi Steve,
Which post were your recommendations in? I went away from Weller due to the high failure rate. They were dropping like flies.

I'm working my way through some NOS 😀 Kester "44".

Hi Joe,
300 KHz would probably be a tube unit. A simple dual 20 MHZ one can be had cheap even new. The used market is awash in scopes. You shouldn't have any trouble finding one.

-Chris
 
#350
barchetta said:
My intial inspection of the board is scary because my work looks good.. but I will heat each one up and mark it with a marker so I miss none..
Click to expand...

What about the joints that you didn't do? Maybe all your new joints are fine and the problem one is one that wasn't associated with the parts that you replaced.
 
#352
Spind: Yeah.. ya know.. I remember when I said here that the right channel got so hot with the previous owner that it toasted the connection to the power switch.. and I said I really will need to heat up all the joints.. Well, I didnt do what I suggested to myself.. so I did it now.. and the result...

IT'S FIXED AGAIN!

LOL!

Yup.. and get this; and you guys will not believe me, after a few minutes (and I repeated this 3 times) the speaker output DC locks down to 0. ZERO.. so what was 30mv right and 10mv left it 0 and 0... I know it seems impossible.. but its weird, and maybe Mr. Pass can explain it I dunno.. but it ABRUPTLY locks onto 0 DC on the outputs.. its weird.

I went thru every single joint and I scraped all the flux off that was sort of connecting things.. I know its not supposed to be conductive but I am tired of gooing up those heat sinks.. and I'd prefer not doing it again! Its messy!

So; I set the Bias back to MY baseline (56mv) and its playing right now.. I think I will just let it play all night like this before I go on further..

WOW! This has been quite the project for me!

ANATECH: I'll try and find that link to the solder station.. its an old ebay auction.. and its a bit too pricey for me.. over $300 used.. and I meant 300MHZ not KHZ.. on the scope.

EDIT: Here are the links from Steve:
Also, if you considered grabbing a soldering/desoldering station it would make your life MUCH easier:

http://cgi.ebay.com/PACE-PPS80A-MBT...1QQcmdZViewItem

http://cgi.ebay.com/XYTRONIC-988D-D...1QQcmdZViewItem
 
#354
Nelson Pass said:
Later versions were, although you could argue that the series
output stage is a cascode.

😎
Click to expand...


Thanks for the advice, Papa.
No, I want to rewrite.
Thanks for the advice, Nelson.

You are not my real Papa, and I have to try plain English,
no joke, no mask, no silly post, no . . . no . . . no . . .

I will take it as a semi-cascoding which is effectively reducing
the distortion, but missing the benefit of low input capacitance.
I will think so unless otherwise commented.


:darkside:
 
#355
A couple of soldering stations that I would recommend:

Hakko 936-12 (can be found new for ~$85 at HMC Electronics and tequipment.net)

If you want to go expensive, take a look at Metcal (never used one, but thats what they use in the labs at work... I own the Hakko).

Chris (Pars)
 
#357
Ok,

A couple of options:

I'd recommend buying a solder/desolder station if you plan to stick with this hobby long-term. I held off buying mine for a long time, and now there's no way I wouldn't have one...

Whichever you buy, buy one that has 60 or 70 watts and is temp adjustable. I'd recommend buying one designed for lead-free soldering just so you're future-proofed. The larger wattage iron will heat heavier joints more easily. You don't need to dial the temp up to 850 degrees just because it's able but it's nice to have the horsepower when you need it...

You're going to have to some homework. I've included a few quick examples and not all included are lead-free versions... Names to search for would be Pace, MetCal, Ok Industries, Hakko, Xytronic, Weller (pro line). I'm sure others will chime in with other decent brands that they've been happy with.

If you buy a rework station, make sure it does thru-hole work. Many of the rework machines only do surface mount so you need to check!

Also make sure that whatever you buy it's ESD rated.

Like anything else, good equipment costs real money. If you can find the stuff used, it's usually the most cost effective solution for us hobbyists - hence ebay.

http://tmt.stores.yahoo.net/reworkstations.html

Solder/Desolder stations:

http://www.howardelectronics.com/xytronic/988dtp.html

http://cgi.ebay.com/XYTRONIC-988D-D...QQihZ002QQcategoryZ109556QQrdZ1QQcmdZViewItem


Solder stations:

http://cgi.ebay.com/NEW-Hakko-Solde...QQihZ010QQcategoryZ109556QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/XYTRONIC-137ED-...QQihZ002QQcategoryZ109556QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/ERSA-Soldering-...QQihZ007QQcategoryZ109556QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/Metcal-MX-500P-...1QQihZ005QQcategoryZ57012QQrdZ1QQcmdZViewItem

http://cgi.ebay.com/XYTRONIC-168-3C...QQihZ002QQcategoryZ109556QQrdZ1QQcmdZViewItem

PS - Nice job on the repair!!!!!!!!! :smash: 🙂
 
#358
Apogee said:
I'm sure others will chime in with other decent brands that they've been happy with.
Click to expand...


I am happy with Kakia (Japanese) lead-free solder.
I use Sn3Ag0.5Cu Flux 3% of 1.0 mm dia for p2p and
PCB soldering with pre and power amps.

I heat up iron at 380 degC.

When soldering, I use my eyes to see whether the base
materials surely suck the melted solder evenly. I easily see
the cold soldering. If the base material is not heated up enough
or dirty enough, the base material rejects the melted solder and
push the melted solder back to the 380 degC hot iron.

To deliver the heat to the base material well, I use driver
type of iron tips.

I more often get non-shining soldered points. But, I don't
believe that is the clear sign of any change in the chemical
composition of the solder. I believe that the mechanical
contact strength and the chemical composition (conductive)
are still there. Any comments on this?


:darkside:
 
#359
Thanks Steve and Bobowana. I am not sure if I will stick to this hobby but I'd like to have something decent so I will start looking.

The 400a ran for 4 hrs last night with 0.01mv dc on average. 🙂 Both sides.. 🙂


So I will try and bias it tonight. If I order a scope today I can do the final testing next week assuming I run into no problems adjusting..

Steve you mentioned 9800mfd for the filter caps didn't seem right (even though that is how one of the two is marked).. what would be ideal for this amp? Can anybody offer some advice? The schematics to not say that I have.

One of the two looks original.. seems stupid to not finsh this rebuild up.
 
You must log in or register to reply here.
Top Bottom