[Hallicrafters] New SR-2000

[Al Parker]

Hi Jeff,
	I have an SR-2000 also, what an awesome rig.  I'm particularly 
impressed with the receiver section, quiet and quite sensitive.
	A cupla quick thoughts on your issues--
	Your idle current it too much now, adjust the bias for abt 200 ma, per 
the manual.  Your increasing idle current could be the bias voltage 
dropping (closer to zero).  Maybe something in the bias supply ckt is 
changing as it draws current for a while.  (I'm not sure why the schem. 
indicates that the bias should be more negative for high power than for 
low pwr, I'd expect it to be the other way around).  Also, (you don't 
want to find this) maybe one or both final has been overheated and 
internally elements are moving as it gets warm.
	Your observed capacitor values and voltage ratings don't look like 
there's a problem, just that somebody has changed them along the way. 
None of the values used should make a noticeable difference.  A higher 
voltage rating is acceptable, and a higher capacitance value is rarely a 
problem (within reason).
	The plate voltage multiplier, those series 1 meg resistors, probably 
have changed value.  The originals probably did, and were replaced by 
the 5 to make up the proper resistance, which has changed again.  Not an 
uncommon thing.  Also they're probably not rated for the voltage across 
them as the originals were.  They drift high and then you read lower 
voltage than actual.  The 15 ohm to gnd (shunt) is OK probably, but 
didn't need to be a 50 watter, it passes very little current.
	Jim's info is great.  Check to see that the factory mods have been done 
in your unit.
	Hope this is some help.
73,

Al, W8UT
www.boatanchors.org
www.hammarlund.info

"There is nothing -- absolutely nothing -- half so much
worth doing as simply messing about in boats"
Ratty, to Mole

On 5/13/2018 9:35 PM, Jeff wrote:
> Hi All -- I'm the proud owner of an SR-2000 -- SN 452002 843004.
> 
> I've got lots of work ahead -- it's cosmetically pretty good, but lots 
> of the standard stuff needs to be done.
> 
> I'm working with Jim's (K9AXN) technical library and trying to soak in 
> as much information.  I brought it up on the variac, and it does in fact 
> hear, although not well.  It also puts out about 600 watts RF on low 
> power, and reportedly has decent audio.
> 
> It's WAY premature to ask for troubleshooting help, since I've not done 
> half the stuff I need to do, but I've got a quick question that I'm 
> hoping might be answered with a simple "duh, RTFM" or other insultingly 
> simple response.  When I hit the PTT on sideband, I see a resting plate 
> current of about 250-300 mA.  I see voice peaks drive it up of course, 
> but then the plate starts drawing current on it's own until the power 
> supply protection trips and shuts it down.  It almost seems temperature 
> related, but I can't say for certain.  It also could be a parasitic, but 
> it's happening on 40 meters and I don't see any evidence whatsoever of 
> overheating or abuse.  I haven't touched the finals or the 
> neutralization since the rig came into my possession -- I'm assuming it 
> worked "last time it was plugged in..."
> 
> Second question -- as I got through the supply, I'm seeing some odd 
> stuff.  First, the bias capacitors (C315,316,317) are two 12 mfd caps in 
> parallel.  It looks OEM, but why not a single 20 mfd (or 22 mfd)? 
> Second, the diodes in the supply are 1N3487. I looked at the datasheet 
> for them, and they show as 1500V .5A units, yet they are used in 
> circuits with far less voltage and current.  Is a 1N4007 (which I have a 
> drawer full of) an acceptable replacement?  Third, the screen filter 
> capacitor (C314) in this supply is a 20 mfd, 500v unit.  The Schematic 
> indicates an 8 mfd.  Critical? Fin ally, the plate voltage meter circuit 
> resistors R313 and R314 have been replaced by what appears to be five 1 
> meg carbon comp resistors encased in shrink wrap coming back from R312 
> (which has been replaced with a chassis mount 50 watt 15 ohm resistor.) 
> My plate voltage reads about 1.2 kV on the meter, so thinking that these 
> resistors have drifted high.
> 
> I'm starting with the power supply of course!
> 
> 
> Advice and war stories welcome!  I'm really excited about this rig -- I 
> never thought I'd be able to get my hands on one.
> 
> 73
> 
> Jeff
> 
> WB3JIH
> 
> 
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