B100R pop on shutoff

[Enzo]

The differnce between the TO218 is essentially, the TO218 is like an overgrown TO220, it has a squarish body and a metal tab full across the top. The TO3P is about the same size, but the metal tab only appears out the upper corners, and the body instead of stopping at the tab, it extends all the way to the top in the center. So the hole is through the body and tab together. Might need a slightly longer screw than the one holding the TO218. This data sheet isn't the best photo, but I think you can see it. Body is shaped more like a tombstone.

https://www.fairchildsemi.com/datasheets/TI/TIP147.pdf

Digikey has thousands in stock. Oh foo, Digikey has a much better photo, here:

TIP147TU Fairchild Semiconductor | TIP147TU-ND | DigiKey



Back around maybe 1970, our band was kinda popular in the Ontario east of Windsor area. We played a lot of high school dances, some clubs, other events. I enjoyed Canada, though it was a huge hassle taking our truck full of band gear over the border each way. The Canadians had their rules, but they were very nice about it. The Canadian customs people reminded me of like navy people - like I was talking to a captain or an admiral. Coming back home, the American customs were total assholes. And that was 45 years ago. Things are WAY more uptight now. Much as I would love to come visit Canada again, I vowed never to leave the USA again, simply because I'd have to come back in through our customs.

[mtlbasslad]

Thanks for the links, I think I see why you suggested TO247 - more watts... if you look at the pic I posted I'm sure there is enough room?

Love to hear more about your band, any links (from 1970 I guess not) or... what style? what did you play?

Yeah we are the polite Canadians... I'll be traveling to New York state next summer for kid #2 wedding (he lives in Texas now, it's complicated) & I'm already getting nervous about the border...
'What is the purpose of your visit' 'Have you ever been denied entry...' 'Have you ever been arrested' 'You need a haircut' 'Is this woman your wife'...

Besides, everyone knows all the terrorists enter USA from Canada, right?

Life was simpler when we grew up, eh...

Hey, if they let us in maybe we could make our way to Michigan?

In your spare time (LOL) look up my wife's vids on youtube... 'Bridge End Dairy Company' & 'Related'

Bye for now

[J M Fahey]

the TIP147 in TO218 is not available... going to check out the TO3P. As for the 'row of transistors' maybe I should change all 4 ? - they are like $2 each...

You seem to be under the impression that *all 4* are TIP147 ; NOT SO.
Even without looking at the schematic, I'm quite certain you have 2xTIP142 and 2xTIP147 .

Also remember to order proper micas and thermal grease.

If the case is TO247 the hole is already insulated (plastic top and walls) and then you just use regular screws, but if TO218 (the "large TO220") , you'll need nylon "nipples"/bushings so the bolt head (or nut if you mount it from below as I do) does not touch the metal tab.

In any case, double check (with amp OFF) that TIP14x center leg (which is connected to the metal tab or back) does not show continuity to ground/chassis/heatsink.

[mtlbasslad]

Hi Juan, nice to hear from you again. In post #51 I stated that there were 2 147's & 2 142's, so that at least is clear.

I'll be careful about insulating & grease, that too I was aware of. Seems like I have unsolder them & test out of circuit - as g1 suggested it may be some other component.

So far I've made a mess of this, but I shall persevere...

Cheers, Lorne & Joanie

[gui_tarzan]

(On the other hand, make some spaghetti sometime, and toss some cottage cheese in it and stir it around. Tastes a lot like lasagna.)

Let's see... pasta, meat, tomato sauce, cheese... yep! Lasagne, spaghetti, rigatoni... You could say the same about Mexican food - tomato sauce/salsa, meat, flour/corn shell, cheese - enchilada, taco, burrito...

It's all good!

[mtlbasslad]

Hi all - so I've been avoiding this for a few weeks, fixing Joanie's Peavey Minx 110 was a priority. Also taking apart the B100R was scaring me. So tonight I took it apart - it was scary.

Here are some pics (I hope)







Hope these pics make any sense. The effin silicone (is it?) everywhere is driving my crazy - it's really hard to remove. What was the purpose of it anyway? - vibration?

So, guess I'll fire up the iron, remove the output transistors & check out of circuit. It has been suggested that the bridge rec or a filter cap might be fried also, any suggestions about what order to proceed?

Always thankful for your patience & wisdom

Lorne & Joanie

[mtlbasslad]

OK ignore 2nd & 3rd pics, I'm not a great photographer - flash etc...

[Enzo]

If it is rubbery, it is silicone, and can usually be peeled off or sliced into smaller bits and peeled off. Of course if you are not removing the parts that are gooped with it, then leave it alone. if it is more stiff or hard, like plastic, it is probably hot melt glue. And that is simple to remove. You spray it with your freeze spray, which makes it brittle and you can shatter it off.

yes, it is there to prevent the larger parts from vibrating and cracking their solder loose.


Just a tip. When I work on a board like that, I almost never have a reason to completely remove it from the chassis. generally, all I have to do is free it, then I can flop it over while still wired to the chassis. Do my soldering and flip it back.

I also see a loose transformer in the photo. WHile there is a heat sink on the board for the power transistors, that heat sink is bolted to the chassis and ought to have heat grease under it. That is because the whole chassis is its heat sink. SO if you plan to power it up while out of the chassis, I would only power it on for very brief periods.

[mtlbasslad]

Hi Enzo

I tried hard to get the board out with minimal intervention, alas she wouldn't come out without removing the transformer.

I understand about the heat sink thing, looking at it I see some grease but it's looking thin - I guess I will add some more.

I've been studying the trace side of the board trying to figure out where to attach to the R66/C38 junction. Two options - 1 - try to attach on the component side - 2 - drill through the board (at somewhere on the trace between R66/C38) & solder a lead there. I know those traces are delicate, should I drill from the trace side or the component side?

The effin silicone is a major pain, even after removing as much as I can there is some clinging to component legs...

If I'm brave enough tomorrow I'll start unsoldering the TIP147's to check out of circuit. I posted earlier that the TIP142's seemed OK, but maybe I should replace all 4 to make sure they are 'balanced' ?

But before that I guess I'll build the light bulb limiter. Sure hope it's just a transistor & not the bridge or the filter caps...

Cheers, Lorne & Joanie

[Enzo]

Your ohm meter will tell you if the bridge or a filter cap is shorted. Of course you would want to remove any shorted TIP guys first.

Um... this thread has been going on for months, and I surely do not recall why you might care to connect something to the junction of those two parts. Whatever you are doing with it, it is simply the -40v rail, so anywhere the -40v goes is electrically the same as the exact point those two parts meet. Hell the left end - schematically anyway - of R66 looks handy, if I needed to pick up negative 40v, I might just wrap a bit of wire around the lead of that resistor and solder it.

Sure, you could drill a small hole, I keep small drills for that, if I recall, #56 was the size I has, though I also have some #62 in the drawer as well. And then on the solder side, sand off the solder mask coating to bare the copper. On the other hand, depending on what you are doing, I might solder a wire to a bared patch of copper on the trace and just run the wire out from under the board. It is a DC power supply lead, so it isn't going top pick up anything or radiate anything either.

[mtlbasslad]

Yep, this has been going on for months... wife, kids, grandkids, my ignorance tend to slow things down a bit. Remember I'm an amateur

Connecting to that particular junction was suggested by km6xz - I realize it's the neg rail. I like the idea of wrapping wire around R66, if I can get the rest of the pesky silicone off. Seems like a simpler way to go than drilling the board.

What a difference between looking at the schematic vs the actual board - all kinds of jumpers & 'opt' parts that are not there. Again, I whine about how close together the traces & parts are, hard for my old eyes & shaky hands.

Thanks for your patience, Enzo & all the rest of you.

[g1]

Try some isopropyl or lighter fluid to get the goop off the component lead. Or hold your breath while you burn it off with the solder iron.
Like Enzo said, any component lead attached to the neg. rail will do.

I understand about the heat sink thing, looking at it I see some grease but it's looking thin - I guess I will add some more.

It is supposed to be a very thin layer, only to fill in the small imperfections in the metal. Too much will impair the thermal connection.

[J M Fahey]

If it's real silicone like Dow Corning RTV and not hot melt solder or contact cement, it's impervious to any solvents and won't notice anything under 400 degrees ... Centigrade

In that case it will even resist scratching (unless very aggressive, removing metal) or sanding.

I suggest you cut it out sliding a sharp blade sideways, "shaving" the part leg as if it were your chin.

[mtlbasslad]

@ g1 - whatever the goop is it resists all solvents...

Got it - thin layer of heat sink paste. Thanks.

[mtlbasslad]

@J M Fahey - yes it must be real silicone, I'll figure out some way to get out...

Meanwhile, Ive taken 52Bill's advice & built a light bulb limiter, I'll try to post some pics (slow cellular internet connection providing)

Next step, pull one of the TIP147's & test out of circuit. Taking deep breath now...