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  #1  
Old 07-26-2017, 04:21 AM
Jon A.'s Avatar
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Quality diodes?

Lots of brands out there, lots of them crap I'm sure. Any recommendations?
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Old 07-26-2017, 09:33 AM
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Look at the data sheet. If the PIV, current, and temp specs meet or exceed that of the original part (or you choose a replacement with the same number as the original), then it should be fine (in some applications above 60Hz switching speed counts).

Silicone rectifier diodes have been in mass production since at least the mid 60's....It is a mature technology that is kinda hard to botch. Any decent sized name that has been around a while should make quality product...If they did not meet datasheet specs they would be out of business in a New York minute.
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Old 07-26-2017, 09:57 AM
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Quote:
Originally Posted by Jon A. View Post
Lots of brands out there, lots of them crap I'm sure. Any recommendations?
Don't recall ever running into any "crap" diodes we bought as parts to replace crappy OE diodes that failed. Like said before, PIV and current ratings that meet or exceed OE are what's important.
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Old 07-26-2017, 12:02 PM
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Quote:
Originally Posted by Jon A. View Post
Lots of brands out there, lots of them crap I'm sure. Any recommendations?
Context? Rectifier, Zener, Detector, HV?

If it's a common rectifier/zener/detector/HV, all brands carried by a distributor are fine. Order from Digikey.ca, pre-pay by money order or check, and you get free shipping....to Canada! Read their terms and conditions page for the juice...I only once have paid shipping to Digikey.....

Don't bother with the lesser voltage rectifiers - a 1A 1000V 1N4007 replaces 90% of the rectifiers you'll encounter (the other 10% are fast recovery types used in scan-derived/flyback secondary supplies or Booted B+ applications.).

As for tubes, I always convert 6X5 supplies to fused protected silicon rectifiers.

HV? I look for NOS silicon or selenium stick types - the Siemens or GE branded stuff. Good stuff, even now. Selenium, you say? Sealed in epoxy, and not the stacked plate low voltage "Oh-my-gosh-get-it-outta-there" stuff. GE and Motorola OEM stuff ( with their TV part numbering...)is what I'm always hunting eBay for...
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Old 07-26-2017, 03:30 PM
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Quote:
Originally Posted by Findm-Keepm View Post
Context? Rectifier, Zener, Detector, HV?

If it's a common rectifier/zener/detector/HV, all brands carried by a distributor are fine. Order from Digikey.ca, pre-pay by money order or check, and you get free shipping....to Canada! Read their terms and conditions page for the juice...I only once have paid shipping to Digikey.....

Don't bother with the lesser voltage rectifiers - a 1A 1000V 1N4007 replaces 90% of the rectifiers you'll encounter (the other 10% are fast recovery types used in scan-derived/flyback secondary supplies or Booted B+ applications.).

As for tubes, I always convert 6X5 supplies to fused protected silicon rectifiers.

HV? I look for NOS silicon or selenium stick types - the Siemens or GE branded stuff. Good stuff, even now. Selenium, you say? Sealed in epoxy, and not the stacked plate low voltage "Oh-my-gosh-get-it-outta-there" stuff. GE and Motorola OEM stuff ( with their TV part numbering...)is what I'm always hunting eBay for...
Not sure what context means but currently I need a 1A 600V rectifier and a 6.8V 1W zener, not to mention a 50 ohm, 5W 5% ceramic cement power resistor, hard to find quality examples of those things. Good to have the goods on the other applications though.

That's a pretty good trick for dealing with Digikey, I'll keep that in mind.

Last edited by Jon A.; 07-26-2017 at 03:33 PM.
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Old 07-26-2017, 07:31 PM
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Don't stop at 600V - that would be a 1N4005, and a 1N4007 (same price) can handle 1000V. I buy them by the thousands (okay, just once, so far) and opt for the lowest DigiKey price - in my case, it was a mini-reel from Diodes Incorporated - I think they were two cents each or so.

Here's some cheapos that will work just fine for any 0-1000V rectification job, 1A max:

https://www.digikey.com/product-deta...7-1-ND/3511542

For the Zeners, I've found that the kits from Banggood/DhGate/AliExpress all are decent enough - you can usually get like 150 Zeners in the popular voltages for 3.99 shipped - to the US. I dunno if China has an agreement with Canada Post about the E-packet stuff.

https://www.banggood.com/300pcs-2V-3...l?rmmds=search

As to resistors, quit looking for old-value resistors - you gotta think "E24" values, so 47 or 51 ohm resistors - and there I pull from old chassis. Generally, I can go up in wattage a bit if size permits on my own stuff, but for others/customers, I go with the correct wattage. If I have to buy, I again look for the lowest price. Square sand/cement "PW" (a TRW/IRC designation) resistors are what I use most - they are getting harder to find, so some overlap into the NTE stuff - and I get them locally.

http://www.ohmslawcalculator.com/e24-resistor-sizes
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Last edited by Findm-Keepm; 07-26-2017 at 07:35 PM. Reason: Added links....
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  #7  
Old 07-26-2017, 07:36 PM
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Will those green wirewound resistors sub for the square cement ones?

By the way, the resistor I'm looking to replace is marked as a critical safety component in the schematic.
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Old 07-26-2017, 07:55 PM
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Yes - it's just a different construction - wind the wire around a ceramic cylinder, dip it in a ceramic paste, and bake.

Note some green resistors are film "MOL" resistors made by either Corning or Mallory. Green was Mallory's color, and light blue was Corning. Easy to tell - smooth in the middle, and matte color throughout. (Brown MOL resistors came from Welwyn - they also made most of the Workman stuff years ago..). The MOLs will work in almost every instance just fine - they are naturally non-inductive, so even better in high freq stuff.
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Last edited by Findm-Keepm; 09-29-2017 at 07:39 PM.
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  #9  
Old 08-04-2017, 04:21 AM
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What's your take on these?

Too bad it's only 40 ohms. It was in a set that was used to death and beyond yet still its resistance is almost dead on.
Attached Images
File Type: jpg 40 ohm 5 watt ceramic wirewound resistor.jpg (33.2 KB, 18 views)
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  #10  
Old 08-04-2017, 08:08 AM
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Ward Leonard Resistor - good company. If you've ever ridden a (electric) train in North America, chances are they made the electric motor braking resistors.

The puke green color is a trademark of theirs - and it's easy to tell if one has overheated - it turns a butterscotch/gold/tan/sand color. Ohmite bought their resistor branch in 1999.

40 ohms is a bit low for replacing a 50 ohm resistor. It's a 20% drop - and most wirewound resistors have a 5 or 10 percent tolerance. Got anything you can place in series with it, say a 10 ohm, or even a 5 ohm resistor? Resistance adds in series....
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Last edited by Findm-Keepm; 08-04-2017 at 08:11 AM. Reason: Added info
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  #11  
Old 08-04-2017, 08:01 PM
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Oh I wasn't about to try to use this one for my application, I was thinking it's a pity I can't use it because it's the only one like it I have. I'd rather use a single resistor, neatness counts big time with me. Besides, the resistor being a critical safety component in the power supply I'm sure to fry something if I try to use it on its own. Looks to me like it's acting as a dropping resistor/voltage divider, whatever it's called in this case. Each end is connected to separate 470uf filter caps and there are wires on each end carrying very different voltages, 82 and 124 if I recall correctly.

Last edited by Jon A.; 08-04-2017 at 08:06 PM.
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