To AB2KG or any others using this amp:

You're welcome Pete. Looks like the forum isn't monitored much anymore. Have you used this linear on CW? I really want to use it on CW at this time. I have a Smallwonderslab DSW-II-20 coming which is a 4W CW xcvr. I then want to get a QRP PSK-31 xcvr and then use the amp for that.

Al - K8AXW

Al,
It will do a fine job on CW. At 4 watts you output will be a little lower than if driven with 5 watts...but who will know the difference. Hi Hi Have fun. It a nice amp.
Pete AB2KG

Does anyone know if the filter board and relays will handle 140 watts? I'm thinking of using this board for another amp project I am working on.

Jonathan
WA3WDK

Does anyone know what the minimum power supply is for this amp ie. how much current it draws with the key down?

Also Mouser apparently quit stocking the heat sink, any experience operating the amp using only the case as a heat sink?

73 John

Nothing magical about the heatsink – it stays cool in SSB service. I suspect the case will work fine. Power supply should be 5 Amps or so.

Jim

Am I blind or is D8 not shown on the parts placement diagram. It looks like it can go somewhere near and parallel to C19? The parts list only calls for 2 T-220 mounting kits. Does D6 not need to be mounted similarly to Q3 and Q4? Thanks /John

Anyway, onward! - Mort Saul

I am currently traveling out of the office and will not return until Tuesday morning, March 2.

I don't have a copy in front of me but as I recall D8 is not on the PC board. It is hardwired directly to the power connector on the chassis. D6 can be mounted directly to ground without any special hardware.

Jim

I completed the amp board and adjustments with approx 30 watts at 14 mhz. When I added in the filter board and tested it, it appeared to work too... relays clicking, etc. All of a sudden, no power output from the amp.... a "small jump" in the watt meter (less than a watt) and nothing. I can hear the PTT relay kicking in. There are no apparent fried/burned parts.
  Amy suggestions on how to trouble-shoot?

rob
n3hu

Rob, I had a similar experience. I haven't had time to troubleshoot but am thinking I may be victim of the problem identified in message #13 re the problem with the Far filter board. Good Luck! /John

Is anyone interested in a group purchase of 2SC2312C to beat RF Parts minimum purchase? I toasted mine when connecting the filter board. Thanks /John

I am indeed interested in a group purchase. How about some teflon wire also. I'd like the heatsink too.

My address is good in the callbook. rcnixon (at) mindspring (dot) com

Russ

I would caution builders to make sure that the chassis surface under the soft thermopads beneath the power transistors is very clean and smooth. I had a nagging "loss of insulation" problem that was resolved when I discovered that a fine, hardly visible, aluminum burr on the chassis had actually cut through the pad to short the collector tab.

Also (by the way) I've noticed that the latest Mouser catalog (Cat. 621) refers to an incorrect illustration and pinout for the NEC relay type MR-82-12USR (K-1 on the main board). The part number for ordering is correct (551-MR82-12USR, and the illustrations themselves are actually labeled correctly.

I have a continuity in the filterboard between the input strip and ground. Can't find any solder bridges. Any ideas? I hate to think of trying to pull the relays. Thanks es 73

Roland,
Scan back to message number 13 it notes an earlier problem with the FAR Circuits board. If not, then perhaps you can isolate the defective relay by removing the solder from the input pin with some soder-wick.

Jim

Anybody know where you can get this heatsink. Seems as though Mouser no longer stocks them. Thanks in advance

Gary