TDI Electronic Load DLP 50-60-1000A Troubleshoot & Repair

Let's get this recently purchased Transistor Devices Inc. 1000 watt electronic load (Dynaload) back to working condition. See what components failed and how to replace them plus a look at the schematic relating to the failed parts. Some overview of the Dynaload's features are also discussed and a final test is run on the unit.

#electronicsrepair #learnelectronics #testequipment

[Ray_of_Light]

I stopped using the 2N3055 in my designs at the time, because when the collector current went above 5 - 6 Ampere, the Hfe dropped from 30 - 35 to 5 - 3. With Ic = 10 A, Hfe = 3.
I switched to the BD142 which had a much better gain curve.
Your wonderful dummy load has - very likely - undergone a thermal excursion which degraded the output transistor. Great job!

[Brian]

For what it's worth - that dark red/brown material you pointed out on those adjustable components is called GLYPTOL. Once the component is properly adjusted the GLYPTOL is painted on and when dry locks the part in place.

[МихаилСеров-юо]

Thank you for your video! Can you please give a link to download the scan of schematic of this great device?

[karlmartell]

What a wonderfull device, wish I had one on my bench. 👌

[charliew.]

Looks like a great piece of kit. I'm currently designing and building a very similar device (with higher ratings) as a University Project. It's reassuring to see how many of the same design choices are present in this 40 year old tech as my designs. I was worried about my 8 x power transistors, but having 22 on the Dynaload you've got certainly put those worries to rest haha.

[splitprissm]

Aren`t the original 2N3055 in the unit likely to be 2N3055H style types (hometaxial), while the modern ON types are likely to be epitaxial types (with completely different specs, especially being too fast for designs that rely on the hometaxial type, and a less tolerant SOA curve)?

..

Could the blue dots be so kind of thermochromic paint?

[InssiAjaton]

I would think the transistors are matched to base/emitter voltages, rather than beta. That is what matters more in the parallel connection.

[andymouse]

External modulation actually means remote control 10 amps per volt ? because nothing is being modulated in the traditional sense I think ? great video !

[darrenmurphy]

strange they didnt use mosfets to eliminate thermal runaway mosfets dominated 1980, s pa/disco amps for that reason and they were more robust 400w rms per channel into shorted wiring and they would survive just fine! , i learned a hard lesson about runaway with a home made 0-30v 3a dual psu using a 4x 2n3055 each output on huge fruit machine salvaged heatsinks, not huge enough if charging nicads for hours!

[zbigniewrichard]

Don't you have a thermal imaging camera? I know it is cheaper to use the fingers, but it's 2024...

[FireballXL]

Surely if they have emitter resistors that may be easier to see heating up with and IR camera.
LOL I should have watched it 1 minute more.
I use this method quite often when you have multiple devices on a shorted supply rail.

[williamkofi]

Please can i get a copy of the schematics ?

[samuelfellows]

4:54 - intake with fans and out the slot at the bottom rear = that cooling/venting arrangement looks and sounds stupid [particularly if mounted in a rack]; the hot air being blown out the slot and takin back in with the fans! “short-circuit” Did they want it to overheat and burn-out in use/a risk🥵😠

[psmamaral]

200+ hfe for 2N3055? Look in datasheet and 100 is maximun (considering error). These transistors are suspicious