Show me your dummy load(s)!

[avionic]

I guess DI is not a good idea..I will crawl back under my rock now....

 

[avionic]

I only found a price on "skygeek". $1200/gallon. Yes, one thousand two hundred US dollars per gallon. If that's even remotely correct...wow.

Uncle Sam probably payed twice that..The **** will wreck a BDU uniform very quickly.And is some real messy stuff.

 

[Ray Gianelli]

Put these together. 1,000 watts @ 8Ω.

 

[AudioWizard]

Here are some of mine;
First up is fan cooled 8 ohm 250watt Dale non-inductive x2, used some LCD Tv feet for away to get it off the floor . I used this one most of the time with the ST 1200a


Next up is neat little load bank, with selectable 4,8,16 ohm settings. I was told that they were made for McIntosh service centers in the 50-60s, but haven't found any information on them to validate that claim. They did come from an old Mac dealer/service center and are about (guessing) 60 watts, very professional looking. I have two of them.


And when need more wattage or different load values? A bunch of 8 ohm Dale's 250 watt.

 

[rottalpha]

Here are some of mine;
First up is fan cooled 8 ohm 250watt Dale non-inductive x2, used some LCD Tv feet for away to get it off the floor . I used this one most of the time with the ST 1200a
View attachment 1485623 View attachment 1485624

Next up is neat little load bank, with selectable 4,8,16 ohm settings. I was told that they were made for McIntosh service centers in the 50-60s, but haven't found any information on them to validate that claim. They did come from an old Mac dealer/service center and are about (guessing) 60 watts, very professional looking. I have two of them.
View attachment 1485642 View attachment 1485643

And when need more wattage or different load values? A bunch of 8 ohm Dale's 250 watt.
View attachment 1485649

YES, somehow I can identify with your solution



I have eight of these 250W @4 ohm Dales and I am going in the same direction....but I just canibalized the aluminum backing plates needed to attach the resistors to the active cooling heatsinks... I will get back to the project soon enough

 

[rottalpha]

Put these together. 1,000 watts @ 8Ω.



View attachment 1485112
View attachment 1485113

I like the two monsters

 

[fill35u]

Coolanol
Is used in the aircraft transmitters. To cool the power supply and TWT's

Surplus 6kW C-band liquid-cooled TWT I'll get around to playing with one day:



Hefty dummy load. Oddball resistances, but easy to trim with lower power resistors:

 

[Bill Ferris]

 

[elnaldo]

Hello. The recent posts about "dummy loads" made me research a bit (since I was offered to buy a couple of large inductive dummy loads, 12" long thick aluminum pipes wrapped with enamel wire, making 8 ohm, and some hundred watts).

Have you tried a circuit like this one, to make a reactive load, simulating a speaker load?
(no affiliation)
https://www.prosoundtraining.com/2011/08/09/dummy-load-testing-large-amplifiers/ (scroll down to the impedance graph)

 

[Hipocrates]

Lets bump up this old thread.

This is one temporary dummy load that I made some time ago but is on my bench since then, is kind of a prototype, 2ch 8Ω 200W (allegedly) 4Ω 300w, mounted on heatsinks salvaged from AVRs, on a old HP computer chasis it have an a array of fans on the back in case things get hot, 10:1 connector (on the right) and 2 for test gear... surprisely works pretty good

Edit... I think I should make a better faceplate for some ''panache"

 

[Reyhifi]

Actually is on the to do list, I have some 50w Dales for now and some of the connectors even the schematic. I’ll try to get it done this weekend. Testing coming up, for some projects.

 

[DEAFASABAT]

This Dale 250 Watt Aluminum resistor is special.
It belonged to James Bongiorno, from his lab.

 

[DEAFASABAT]

Hello. The recent posts about "dummy loads" made me research a bit (since I was offered to buy a couple of large inductive dummy loads, 12" long thick aluminum pipes wrapped with enamel wire, making 8 ohm, and some hundred watts).

Have you tried a circuit like this one, to make a reactive load, simulating a speaker load?
(no affiliation)
https://www.prosoundtraining.com/2011/08/09/dummy-load-testing-large-amplifiers/ (scroll down to the impedance graph)

No, but back in about 1984 I repaired a Fender Super Reverb Amp at an alternate location from my shop. When it was completed I needed a dummy load to do the bias adjustment and full power test.
All I could dig up was a new 500' roll of 16 ga. stranded wire. I removed enough wire to adjust the resistance to 4 ohms. Being it was still on the original metal spool and a heck of an air core inductor, so I was concerned it might ring like a bell, but it did not. Mission accomplished.

 

[DEAFASABAT]

All I know is they blow, everybody blew theirs. The way they do their rating is not good. That's the bottom line, they blew so bad that's why they belong in the history in the last 30 years already. If their advertized rating is anything close to the real life, they should had stood up to a Fender Twin with only one speaker. I doubt they can last 30 minutes of the full on Twin Reverb.

Those K or D120 might be able to last a little more if you run just say 60Hz sine wave. The voice coil is 4" wide with paper voice coil form running in a very narrow gap. If you run one low frequency, it might hold up, but if you over drive with clipping with a power chord, the voice coil just jump and bent out of shape. The diameter is so large it doesn't take much to get out of shape and start rubbing the frame and destroyed. It was such a bad design even a novice can see it.

I am talking as a working musician in the real world that see all the bad JBLs back it the 70s. Funny when I went to the tech, he had a big bucketful of bad JBL 4" voice coil cut out he even gave me a few to take home. You look at one and you'll know exactly what I mean and why it failed, how easy it bent out of shape.

More importantly, they don't sound good for the rock over drive distortion. They might be popular for the 60s surf music like the Ventures and Beach Boys with crystal clear guitar sound with reverb, but when the hard rock music came in style, JBL just did not cut it. The middle aluminum dome was the problem. It's more a full range speaker than guitar speaker. When over drived, it sounded more scratchy. You want the Celestion Green Back type of speakers for rock. By mid 90s, JBL was non existence.

In 1975 I bought a used JBL K130 off a friend who was a very hot guitar player. He played loud through a Sun Model T amp into just that one K130. It still sounded OK but I thought it should have been more efficient. Checking with an Ohmmeter showed that its DCR was about 40 Ohms.
Harman had just recently opened their Northridge facility, so during a trip to LA I dropped it off there for a recone. Would you believe, it was just $50, done right there at the factory.
When I picked it up, the tech said "Hey, check this out". The old voice coil and former looked like that piece of aluminum foil you left on the grill till there was little left of it. And even in that condition, the big JBL probably still sounded better than some cheaper new speakers.

 

[AudioWizard]

Here is some of my extra 8 ohm Dales.

 

[audiodummy]

Inductance be damned... my dummy load is over 2:1 SWR at 440MHz ... Sigh. Need to get better resistors...

 

[Bill Ferris]

Inductance be damned... my dummy load is over 2:1 SWR at 440MHz ... Sigh. Need to get better resistors...

Those damn VHF/UHFs will mess with you every time !

Cantankerous electrons !

 

[Reyhifi]

I just order a few parts, to build the dummy load setup.

 

[GKTAUDIO]

One gallon new paint can with heavy rubber exterior coating loaded with 2 water heater elements, filled with mineral oil and connected to vented expansion bottle. Sits in a deep tray.

 

[whoaru99]

One gallon new paint can with heavy rubber exterior coating loaded with 2 water heater elements, filled with mineral oil and connected to vented expansion bottle. Sits in a deep tray.

I put mine in a 5-gal pail of water. I just dump the water in the garden when I'm done.