Badge, it looks like you need to re-touch all your solder joints with either a bigger tip or a hotter iron. I see possible cold solder joints all over the place. They need to look smooth and glistening wet like melted ice cream. You have pasty rough looking joints which indicates solder barely had a chance to melt. A lot of the holes for the resistors should have solder filled in tonthe gaps. I can see black space in between the leads and the hole. A fat chisel tip often allows more heat to flow. You don’t want to use a micro precision tip here. Also good quality 60/40 solder is important. Use Pb /Sn solder. Forget about Pb free stuff.
You are correct. I did use a fine tip on the iron. The solder pads are quite small. I will hit them again and see if my problem goes away.
Data Sheet isn't helpful.
However, since it's designed to be a power supply filter choke, I would not worry about it for MOFO applications.
https://www.mouser.com/datasheet/2/643/SC-1134958.pdf
I would contact the manufacture if you are curious.
However, since it's designed to be a power supply filter choke, I would not worry about it for MOFO applications.
https://www.mouser.com/datasheet/2/643/SC-1134958.pdf
I would contact the manufacture if you are curious.
Pass DIY Addict
Joined 2000
Paid Member
Has 40% more inductance than the Microwave Oven Transformers that have been floating around, similar resistance, half of the current carrying capacity, and costs 2x as much. I would be reluctant to use a 4A choke with much more than 2A of current for continuous duty, though perhaps it's worth a try. If you use them, I would keep an eye on the temp rise of the choke.
My MOT has 56uH, 0R56 resistance, and is rated at about 7.5A. Running it at 19v and 3A produces about 10c thermal rise in the choke. I could probably increase the bias more, but I'm not going to.
I think it will work, though I'm curious about its thermal behavior with respect to its current rating.
Pass DIY Addict
Joined 2000
Paid Member
Check your voltage drop across your choke. If this is too low and won't adjust up with the pot, then you've blown your output mosfet. This happens when you unplug your DC power supply (on the DC side into the amp, not on the AC side at the wall socket). I did this a few times before people here pointed out my error. I blew the mosfet AND the zener, both needed to be replaced.
Adding a 1kuF (or somewhat larger) cap at the DC power entry will save your mosfet from improper power disconnect.
Pass DIY Addict
Joined 2000
Paid Member
Maybe just my lack of experience running a choke at or close its rated current. I was trying to apply Nelson's "belt AND suspenders" approach to engineering for the long haul
> The Bel is 4A capable. Am I missing something?
It appears to be rated for heavy use in large DC power supplies.
A quick estimate of losses suggests, at 4A, 13 Watts of heat in 50 square inches of surface. It will run warm but far from hot. I believe the rating is plenty conservative.
Considering that 4A and 8 Ohms scales to 32V peak, maybe 35V across the MOSFET, which comes to 140 Watts of MOSFET heat to get rid of, less-greedy builders could look at the _CH-2_. At 2 Amps we are thinking 16V, 32-36 Watts dissipation to handle. And the choke is 2/3rd the price.
It appears to be rated for heavy use in large DC power supplies.
A quick estimate of losses suggests, at 4A, 13 Watts of heat in 50 square inches of surface. It will run warm but far from hot. I believe the rating is plenty conservative.
Considering that 4A and 8 Ohms scales to 32V peak, maybe 35V across the MOSFET, which comes to 140 Watts of MOSFET heat to get rid of, less-greedy builders could look at the _CH-2_. At 2 Amps we are thinking 16V, 32-36 Watts dissipation to handle. And the choke is 2/3rd the price.
Pass DIY Addict
Joined 2000
Paid Member
Exactly, PRR pointed this out to me. A small cap on the DC input damps the collapse of the coil just enough for the mosfet to survive.
Sure! New looks nicer than recycled like mine
I put a coat of paint on mine which brings them closer together in appearance.
It's not about the look. It can be dangerous if you don't know what you are doing. Also finding the mot that work in this application isn't easy.
I tried and wasn't able to discern between an acceptable mot and one that isn't.
Here's the thing. Sometimes it's just better to pay up if you can.
I tried and wasn't able to discern between an acceptable mot and one that isn't.
Here's the thing. Sometimes it's just better to pay up if you can.
Pass DIY Addict
Joined 2000
Paid Member
You can look for "MD-803AMR" on ebay. I have 4 of those and they work at 5amps even. circa 60-70mH and DCR around 0.5ohms. Vunce has 6 I think...
Just tape up the thin secondaries and use the thick faston tabs on the primary. Easy to do. Usually a good deal at $25 shipping included.For example:
5RR53 EMERSON MW9325SL MICROWAVE OVEN PARTS: TRANSFORMER, MD-803AMR-1, FWU, VGC | eBay