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Somebody dropped off all this junk!




 
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Author Topic: Somebody dropped off all this junk!  (Read 11784 times)
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Patrick J. / KD5OEI
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« Reply #25 on: November 29, 2008, 02:13:54 AM »

Update on the shack.

Thanks to my apprentice, we got started at 11AM and cleared out over 120 SQ FT of space in the shack and also brought in a rack and stuffed it full of low voltage power supplies for in case of having to use or work on transistorized radios. It was a job because these things are not to be taken lightly. To fill up the rack, we laid the rack on the floor face up, and dropped the supplies in. So, from top to bottom:
12V supply additional filtering - basically a chassis same as the 12V supply, with L&C, less PWR XFMR
12V supply additional filtering - basically a chassis same as the 12V supply, with L&C, less PWR XFMR
12V supply  - does 12.55V @ 37A as measured - It's from some Motorola set.
0-35V 15A regulated supply - a monster full of those big round geraniums.
24VDC 25A Sola resonant regulator supply
24VDC 25A Sola resonant regulator supply (put in parallel with same above for 50A)
48VDC 4A Sola resonant regulator supply
The holes were not for the usual 10-32 screwes so I rant a tap through them to make ready. The drawers were already in, so I left them. I can put power cables etc in there. The main disadvantage is the rack is now front heavy so I will want to bolt a couple if 2x4's under it that stick out in front and help revent any unfortunate tipping.

To erect the rack, we used a hoist with a block and tackle tied throughthe top frame of the steel rack. Ye Younge Apprentice could not do well with the hoist, so I provided the required ballast to pull the rope down. This is a very easy way to fill up a rack, alot easier than supporting several 50-80LB equipments by hand and trying to stab the screws.


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Patrick J. / KD5OEI
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« Reply #26 on: November 29, 2008, 02:15:41 AM »

Jaws II Update

Back to the JAWS II amp - we went and got it from storage and it was 11 PM, so for some reason, probably because he is 20, he had to go over to his YL's house. She is very nice, and when she calls and he says we are working with electrical equipment, she does not complain.

I removed the covers from the power supply, as the previous owner had bragged on it alot, telling me about a Dahl transformer, etc. I didn't find PWD iron, but it was still pretty large.

The power supply has seen a few mice but not too bad and the rectifier diodes seem to have been hot and show deterioration and cracks around the terminals. The solder was so hot it has loose joints. This could have been the reason the amp was put out of service. I believe I will replace them before doing anything else.

The architecture is a full wave voltage doubler with a 14 capacitor bank of 800uF/450V capacitors (57uF at 6300V). The transformer has these specifications:

pri: 220V 50/60Hz, 1070WV to GND
sec: 1760V/1.53A (2694VA), 6420WV to GND, (10 Ohm measured DCR)
Langeview MFG corp. L-1527 Grade 1 Class A

It would be interesting to know what the transformer was from.

The transformer appears to have an impedance of 18 Ohms. Based on that, Duncan Amps PSUD II indicates that this power supply might provide these conditions:

4237VDC @ 2.057A (RL=2K)
4389VDC @ 1.463A (RL=3K)
4484VDC @ 1.121A (RL=4K)
4548VDC @ 0.909A (RL=5K)
4594VDC @ 0.769A (RL=6K)
4657VDC @ 0.582A (RL=8K) (2710VA - possibly near a realistic CCS value)
4699VDC @ 0.470A (RL=10K)
4762VDC @ 0.317A (RL=15K)
4798VDC @ 0.239A (RL=20K)

However, much of this simulated information rests on the transformer's assumed impedance and its behavior when overloaded. The program does not take into account overloading's effect on the core.

Real performance can be arrived at accurately only by testing later and like everything else, probably won't be as good.

AM performance also faces limitations from the 3CX3000.
The datasheet indicates these values for carrier conditions in AM Grid-driven amplifier service. The Carrier operating conditions do exceed the power supply transformer VA capacity by 10% assuming no losses elsewhere. I don't know what will happen with modulation. I have not checked the size of the 220V circuit breaker on the front panel.

Plate voltage = 4000V
Zero Signal Plate Current = 0.25A
DC Plate Current = 0.74A
DC Grid Current = 0.13A
Peak RF Grid Voltage = 85V
Peak Driving Power = 11.5W
Plate Dissipation= 1830W
Single Tone Plate Output Power = 1130W (Carrier, so PEP would be 4520W)
Resonant Load Impedance = 1750 Ohms
Peak RF Plate Voltage = 2000V

For practical purposes, I'm sure the power supply and amplifier will idle along easily in any mode at the full power permitted in the Amateur Radio serivce. That's all I really wanted, a linear amp that would take AM service at the legal limit and not cry about it.

reforming the caps in the power supply:
http://amfone.net/Amforum/index.php?topic=19257.0


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« Reply #27 on: June 15, 2009, 10:34:25 PM »

Today I took the amp to task. There are a couple of issues besides some missing parts.

But first I want to comment on the cathode compartment. It is amazing. The first thing that caught my eye was a 50 amp B&W filament choke. It's huge, almost 3" diameter and 8-9" long. The tank circuits for the cathode drive (I was hoping it would be a swamped grid driven unit) are all wound on 1/2" diameter ceramic or fiberglass forms with slugs in them. The smallest coil wire I saw looked like #14. Many were teflon insulated, as was all the wire going from the big ceramic bandswitch to the coils. It looks like a pi network. All bands except 160M have a tank. the 160M band goes straight through. I think it might be because the coil form could not hold enough wire turns. 1 out of the 6 is not wound. The fimament connections and socket are very well made of heavy plate. Between the plate for the outer filament ring and the plate for the inner filament stud are four 1000pF doorknobs. As if this were not enough, the 2" of thick straps between the filament choke and the socket is terminated at the choke with a huge dipped mica cap. I know I should have the appropriate pr0n, later I will take some.

The issues I found are the tuning and loading caps. Someone mentioned before they looked crooked. The top one seems OK, but the bottom one is about 1 degree off. It might be because the holes for the dial turns counters were off, I cannot say. The top one turns easily enough but the bottom one is harder to turn. Maybe because of the angle or misalignment.

The turret-style metal part on the snout of the tuning cap is fairly loose. The one on the loading cap is tight. Both can be turned. These are the items the shafts emerge from.

1. are these supposed to be loose?

2. how do you adjust them?

3. what is the deal on them? - besides protecting the bearings or whatever. Are they to be oiled or anything?  There is a small hole in the side of each one.

the attachment show the kind of caps in the unit. It is more like the tuning cap in appearance.

any advice on this would be welcome.







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