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Reviews Categories | Amplifiers: RF Power - HF & HF+6M | Amp Supply LK-500-ZB Help


Reviews Summary for Amp Supply LK-500-ZB
Amp Supply LK-500-ZB Reviews: 18 Average rating: 4.8/5 MSRP: $1,295 in 1988
Description: Runs a pair of 3-500Z tubes, Legal Limit output, built like a tank! Covers 160-10 meters.
Product is not in production.
More info: http://k4icl.com
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NA1A Rating: 5/5 Aug 23, 2013 06:31 Send this review to a friend
Super Amp  Time owned: 6 to 12 months
This review is for an LK-500ZC, not ZB or ZA model. The ZC is the latest of the series as Danny placed QSK T/R vacuum relay, 3KVA on the PS and a few other re-finements from the ZB model.
Amp runs really smooth, quiet, lots of power. I'd say amongst the 3-500Z type amp, this is one of the best ones made. It is like an SB-220 on steroids.
 
W5LW Rating: 5/5 Nov 29, 2011 15:58 Send this review to a friend
LK500ZC Works Great  Time owned: 3 to 6 months
I purchased a LK500ZC that had a bad plate transformer and badly butchered ALO board and QSK board, I took the ALO board out and put vacuum relays in place of the QSK board. I used an external toroidal transformer I had for the plate and it works great now. 1.5KW out on 20 and 75, I run it at 1KW as a norm. If you can find one buy it, If you have one and don't want it I'll take it. If you need one repaired let me know. A great amp and as already said if Alpha made a 3-500Z amp this would be it, I have a Alpha 78 also and the LK500ZC is just as good.
 
W7RF Rating: 5/5 Jan 27, 2009 16:45 Send this review to a friend
Amp Supply repairs  Time owned: more than 12 months
I just got finished with a total refurb of my LK-500ZC and used Al K4ICL for some advice and repair info. See him at www.k4icl.com . He is the new "go to" guy on all Amp Supply amplifiers and has taken over for Bill after his passing. Friendly and informative on the phone, he seems to know what he is doing. If I didn't do the work myself, I would definately trust this guy for my amp work! I added a step start, HV current limit resistor, HV glitch resistor, new AG6K type parasitic suppressors, replaced all HV electrolytics, all new equalizing/bleeder resistors with new type MOF (Metal Oxide Film, do not use carbon!). My old carbon resistors had two that had more than doubled in value and one was open. I replaced the HV wire from the ps board to the bottom of the plate choke, I didn't like the thin insulation of the original. I remounted the DC block to use more nichrome wire between it and the plate choke. Also remounted the VOX/QSK switch to the front panel right above the H/L air switch. I always hated having to reach around to the back to switch from standard semi break-in to full QSK. I raised the fan slow-down resistor as it was burning the circuit board because it was mounted right on top of it and there was no space for airflow. One other thing I might mention is that I removed 2 extra In parallel) resistors in the Grid Shunt because they did not appear in the scematic. I returned it to what the manual says. When I did that, the grid meter barely moves with full drive and even if I mistune the load control to be "light" (MORE capacitance) loading, which should bring up the grid current quite a bit. Putting those resistors back should make the meter operate properly in the grid position as it did before. I really enjoyed this project and will keep this amp for a while. On 160M the output with about 90-100 watts drive is about 1100 watts, 80-40-20-15M is about 1200-1400 watts, 17M and 12M WARC are still over 1KW as is 10M. Trust my measurements as they were performed into a special Radiodan modified multi-range Bird 43 into a 50 ohm dummy load. Multi-range 43 Wattmeter calibrated with a Bird 6091 calorimeter. I like this amp as it is quiet in the low speed air mode and is very stable with these mods. 73, Dan W7RF
 
W0FEN Rating: 4/5 Nov 25, 2008 10:54 Send this review to a friend
LK-500ZC  Time owned: more than 12 months
This amp would rate an 5-GREAT!- if not for one thing. I have had at least 3 sets of tubes in it and every set has had the problem of the solder running out of the 3-500Z pins. It is an easy fix to resolder the pins. That is not the problem. This should not happen. The SB220 had the fan set up to cool the pins but this amp doesn't. I will keep this amp because it is the only one I have that has 160M on it. I will use another amp for all other bands.

I agree with all other positive reviews of this amp except for the above.

w0fen
 
K6TLA Rating: 5/5 Jun 24, 2006 23:45 Send this review to a friend
Solid Amplifier  Time owned: 6 to 12 months
I had been after this amp for years before finding one late last year. Construction is solid, the tank circuit is well built, and the bandswitch is impressive, kind of reminds me of the Daven pots of old. Lets not forget that this box includes 160 meter operation as well. Mine came with the 10 meter modification in place. The massive Peter Dahl transformer should last longer than I will. Frankly I bought the amp as something that I could keep for another 25 years and initial experience says that it will last at least that long. There's no 220 in the shack so it has been set for 120 volt operation. The amplifier works perfectly well on 120. This desktop box is a keeper. Not many seem to be listed for sale. Most owners probably see the quality and value here and keep them over the longterm. The LK-500 series amplifiers are highly recommended.
 
M5TAW Rating: 5/5 Mar 12, 2006 13:00 Send this review to a friend
Outstanding amp  Time owned: more than 12 months
I bought the 500ZA model second hand approx 18 months ago. It has served me very well during this time. The build quality as mentioned by other reviewers is first class. There is no comparison between this and Ameritron for example (I currently own and have owned various Ameritron amps in the past - I have nothing derogatory to say about them). It works very well on all bands including WARC. Approx 20 watts in produces 400 watts out - UK limit :(
and 60 watts provides 1000w out (limit of my dummy load).
They are quite rare in the UK and definately a serious alternative to TL-922 etc...
 
AA4SY Rating: 5/5 Apr 23, 2004 11:23 Send this review to a friend
Great AMP!!  Time owned: more than 12 months
I have the LK-500-ZC and have been very happy with it. (300 + DX confirmed) It has blown a capacitor, and I spoke to Bill at Omega Electronics (http://www.omega-electronics.com/home.html) and got the scoop on repairs and mods.
Turns out Bill worked with AMP supply before the owner got out of the AMP business, so he really knows these AMPS!
If you have a chance to pick one of these amps up, BUY IT!! You'll get a super amp for the price. It's a real workhorse.
 
KC2LCZ Rating: 5/5 Nov 25, 2003 00:47 Send this review to a friend
LK-500ZC  Time owned: 6 to 12 months
I'm getting legal+ on all bands excluding WARC. It uses top notch components and is easy to tune. A new amp of this quality utilizing 3-500z tubes will cost close to 3k and may not provide legal limit. I sent the amp down to Bill at Omega Electronics to have a vacuum relay QSK circiut and a step start added. While it was there he also replaced the aging wiring harness and noisey fan bringing the the amp to "like new" condition. The LK-500ZC will normally sell for under $1,000. on the used market. Big bang for the buck! If you can find one grab it, you won't be disappointed.
 
WO2E Rating: 4/5 Sep 9, 2003 19:02 Send this review to a friend
LK-500ZC  Time owned: more than 12 months
I HAVE THE LK-500ZC THE PLATE TRANSFORMER WENT BAD. I SALVAGE A PLATE TRANSFORMER FROM AN AMERITRON AL-1500 AND A SEPARATE ENCLOSURE HAD TO BE BUILD TO ACCOMODATE THE BIGER TRANSFORMER I SET IT UP FOR 120 VAC.I USE THE SAME FILTER CAP BOARD ETC. BUT WHAT A DIFERENCE NOT TO BLOW THE CAPS I USE A VARIAC HOOK TO 120 VAC WITH JUST 105 VOLTS IT GAVE ME ALMOST 3800 PLATE VOLTAGE AND JUST 45 WATTS INPUT IT GAVE ME 1200 WATTS OUT. I DID NOT WENT OVER THESE NUMBERS THE HOUSE CURRENT WITH 120 VAC WAS NOT HAVING IT AND FILTER BOARD ETC WAS NOT SET UP FOR THE EXTRA LOAD. BUT THE LK-500 REALLY KICKS A$$ WITH THIS PLATE TRANSFORMER SET UP FOR 220 VAC. NOW I WOULD NOT BUTCHER A CLEAN LK-500 THAT WAS WORKING 100% ESPECIALLY WHEN ANY MOD WOULD REDUCE ITS VALUE. OVER ALL ITS A GREAT AMP AND EASY TO SERVICE AND SIMPLE CONSTRUCTION AND IT WON'T BREAK YOUR POCKET. I LIKE IT AND STILL USED AFTER 8 YEARS.
 
W1ES Rating: 4/5 Oct 17, 2002 08:43 Send this review to a friend
Good Amp for Low Bux!  Time owned: more than 12 months
Bought mine back in the 1980s and have used it for DXing and contesting all these years. It's built very well and has been a real warhorse!

The shortcomings, some of which have been mentioned here by others, are the QSK circuit (you can't run the amp in standby if it's wired for QSK without an annoying sidetone), high filament voltage (corrected), king-kong band-switch detents(corrected-- removed one of the two ball bearings-- what a difference!)and lack of step-start for the PS. THere is plenty of room inside to do mods, however, and I've done several: extra cooling holes to the outside through a level beneath the deck, voltage-dropping wire to bring fil voltage to 4.75V and AG6K mods to anode & grid circuits.

With a good QSK circuit (which I swear I've been meaning to get around to playing with for 15 years but haven't) this represents the absolute best bang-for-the buck out there! Because the brand is an orphan, you can get them for a lot cheaper than they should be selling for! Frequently, you can get these for less than an SB-220 and it is a MUCH (I can't stress this enough!) better amplifier that also does 160m!
 
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