Fired up the Cheyenne tonight - it'll need some work

[AF9J]

Hi everybody,

I fired up the Cheyenne tonight, into a dummy load, to give it a test drive.  In a nutshell, she's going to need some work. 

The antenna relay works fine.  In looking at the way the needle moves on my Diamond SX-1000 wattmeter, on voice peaks, I seem to have OK modulation.  BUT there are some issues I have to take care of.  Driver current is way off.  From what I could understand from the manual (it's kind of lame, and doesn't even have a dedicated section in it with a clearly spelled out tuneup procedure; I had to sort of determine it from my own experience with tuning up other tube rigs, and deducing the final alignment procedure given in the manual, for when you're done assembling the rig), grid current is supposed to be about 3 mA - I pegged the grid meter needle, and as a result, couldn't determine a drive peak.  Power output is also low.  I should be getting about 30-50W on peaks.  At the most, I'm getting about 10W.  Also I will have to check the spot function, with my SX-96, hooked up to the antenna jack on the Cheyenne.  I was hearing a spot signal, but it was more of a hiss, than the zero-beat CW-style note I remember from my HW-16.
 
My biggest concerns, are the power output, and the driver issues.  There are several things I will have to check.
 
1.    The VFO, and/or band pack tuning coils could be misaligned.
2.    The final, and/or driver tube could be going south.
3.    Some of the components could be failing.
4.    The power supply could be part of the problem - when I was troubleshooting the power supply on Saturday, I noticed that the no load HV B+ was only 550V (it's supposed to be around 800V).  Most of the caps in the power supply are the old fashioned cardboard tube types.

73,
Ellen - AF9J

[W9GT]

Hi Ellen,

Sounds like a little troubleshooting ahead.  You might find that the grid current is not really an accurate indication.  It may be resulting from a defective meter shunt in the metering circuit.  It is not unusual for that to happen.  Many times resistance values in vintage gear will change over time.  Might I suggest that you check the metering circuit?  Also, it sounds like a good possibility that you may have some leaky electrolytics in the power supply, resulting in low output voltage.  Are you noticing any heating of any of the caps?  Good luck with your project.  I'm sure that you can get plenty of assistance on this site.  Hope to hear you on the air one day soon.

73,  Jack, W9GT

[AF9J]

Hi Jack,

I was hoping I could get away with the low HV value, since the Cheyenne only requires about 600V for its HV B+.  Obviously that's not the case.  And under load, the HV B+ is probably quite a bit lower.  As it is, it looks like the largest of the HV caps in the power supply was replaced some time ago.  I'll have to check out the meter shunt resistors.  So, for now, I'm stuck with the FT-897D (a mediocre AM rig at best) for AMing.

73,
Ellen - AF9J

P.S. - cute looking Jack you have.  One of my coworkers does Jack Russel rescue for southeast Wisconsin.  She also has two of her own: Smudge (a broken coat male who's about 35 or 40 pounds); and Stitch (a petite smooth coat female [she weighs about 13 pounds], with a Napoleon complex).

[W9GT]

Ellen,

sidenote about my dog...sorry for off topic

Thanks....Nipper is 11 now, but just as ornery as ever.  He weighs 14 or 15 lbs soakin wet.  He thinks he's a Doberman, unafraid of big dogs, but scared to death of thunderstorms, quite protective(especially of the XYL), and very intelligent.  One of the most affectionate dogs we ever had.  Jack Russells, however, are certainly not for everyone.  They are one of the smartest breeds around, but they definitely have a mind of their own and their priorities do not necessarily coincide with their human caretakers!  Nipper is a very adept hunter.  He stalks squirrels and looks like a cheetah or something with his straight back, pointing stance, and sneaky manner.  He also has managed to dig up three ground moles that were destroying our lawn.  All in all he has been a lot of fun and a great companion.

73,  Jack, W9GT 

[WU2D]

Hey Ellen,

You are only a few dB's off as they say. Start looking for dB's! They could have rolled out of the cabinet onto the floor when you had it apart!

Usually there is one big offender like a bad contact or main tank bypass cap unsoldered(my Apache) or a completely mistuned low level stage.

Then there are a bunch of small - "death by a thousand cuts" types like the cruddy socket RF grounding and bypassing in my Apache or a soft driver or low Q tuned circuit, Bias levels, bad bypass caps, resistors drifting in value etc...


- Dogs and Cats

I have three cats including one who likes to hang out in the shack. He was situtated on a comfortable place in back of an ARC-2 miltary transmitter which I had just put on the bench. This unit which has a particularly impressive dynamotor blower, was getting its maiden smoke test. When I let that thing fire up the loud dyno blasted him. He did not even move. He just made a face like like K4KYV as if to say "what the H#$% is wrong with you?

Mike     

[kf6pqt]

Ellen, you're savin' me a bunch of work! I'm just keeping notes of your Cheyenne troubles.   Mine showed up yesterday, the rotating dial drum will need some attention, maybe a re-stringing, but the rest of it is in nice shape.

Unfortunately its going to be a while before I get to it, my new dx100b has rapidly deteriorating audio, and I've ruled out audio tubes and mics... not sure if I've mentioned it on here, but thats my bad news and what I'll spend most of my radio time fixing.

Good luck, and continue keeping us posted!

-Jason kf6pqt

[AF9J]

Hi Guys,

Mike, maybe you're right, a few dBs fell out when I pulled the chassis out of the enclosure.   I have  cats too (two of them).  Both of my cats like to hang out with me, when I'm either operating, or working on radios.  So, they often get in the way.  That happened last night, when Sugar (my little tortie), jumped up on the table, while I was trying to solder up the mic cable, to the connector, to get some loving from me.  I could have shoved her off, but it's kind of hard for me to do.  I help out at a cat shelter, and oftentimes see abused and neglected cats.  Sugar was abondined outside of the shelter, in a taped up box, on a 90 plus degree June day 2 years ago.  I think Sugar was abused by her previous owner (she is easily frightened into hiding, if you apporach her too quickly [I think she sees it as being aggressive]), so I let her have some of the loving she didn't get in the past.  Hopefully, my Cheyenne issues will be few, and I won't end up having to just about rebuild it.

Jason, glad I could be the Cheyenne beta tester for you.  So your DX-100B is still giving you problems - that's uncool.  Is it possiblre that the mod transformer is failing in it?  If the windings are starting to go, it would explain why the audio is getting worse as you use it.  Good luck fixing it.

Well, I'm out of here.  Work's done for the day.  When I get home, I'm going to see what my cap values are for the power supply, and place an order with Mouser for some new caps.

73,
Ellen - AF9J

[w1guh]

One tip about tuning up those Heathkit controlled carrier rigs...use a scope to adjust the modulation.  If you believe the manual and tune it up as it says, you'll be distorted.  So use a scope and adjust the mic gain for 100% modulation and you'll sound very good.  No, the meter won't bounce, and yes, you'll be running "less power" (sorta)...but...you'll really sound good.

Having said that...the Cheyenne is a very good radio, and I'm envious of your getting to put one on the air.  Have fun and enjoy that.  It's a "junior Apache."  Pretty much the same RF chain but with only one 6146, and, of course, with the screen modulation.  But...it fhat screen modulation is adjust properly...you'll sound really good.  Enjoy!

73,

Paul

[AF9J]

Thanks Paul,

Well, as I mentioned in Jason's thread about his DX-100B, I realized that the cap that was in the bottom of my HP-23A power supply was an add-on, or a kludged together repair for C1 (which may be open line), in which C1 wasn't even disconnected.  I ordered new caps for the power supply. 

Guess what Jason?  Nobody sells 125 microfarad caps with 450 or 500V ratings, much less in a twistlock rating.  Not Mouser, not Digikey, not Just Radios.  I had to settle for 120 microfarad caps.  You can get either 450V rated ones from Mouser, or Digikey, or 500V rated ones from Digikey (they're about $5.40 each - Mouser will special order them for you, but does not carry 120 microfarad  500V rated caps).  I bought the 500V ones from Digikey, for a little bit of a safety margin.  I also bought replacements for the cardboard, 20 and 40 microfarad electrolytics too.  Digikey doesn't sell these, but I bought 200V rated 22 microfarad caps (I'll wire 2 of them in parallel for 44 microfarad).  The only bummer, is I checked this morning, and discovered that Mouser sells 20, and 40 microfarad electrolytics, with 150, or 450V ratings.  Ugh!  Oh well, that's what happens, when it's late at night, and you don't feel like messing around with ordering things from different parts sources. 

73,
Ellen - AF9J

[kf6pqt]

Ellen,

if you can spare the time, could you cut-and-paste the caps you ordered from Mouser in a reply or a PM for me? My HP-23 is exactly that model, the 1st one... I've powered it up with the Eico 7-drifty-3 it came with, like twice... no hum, but I want to recap the thing anyway and have it be the general-purpose workhorse it once was.

Thanks!

-Jason kf6pqt

[AF9J]

No Problem Jason,

I'll send you the parts numbers when I get home later tonight (after I help out at the cat shelter, after work).  Oh, BTW, you might want to also check the 2 watt 100K resistors.  They can get out of tolerance over time.  I looked on Digikey's website, and they only offered the 2W versions in metal film(probably fine for use with the supply).  Also, they had a minimum order quatity of 5 or 10.  Ugh!  I might check Mouser tonight, when I get home.

73,
Ellen - AF9J

[W1RKW]

Ellen, Jason,
Try contacting MCM Electronics and East Coast Transistor for these capacitor values.  Last I knew they had these values in close proximity to those you're looking for in radial and axial lead.  No twist locks however and no need to parallel or series them either.  Also try Newark.

[AF9J]

Hmmm good idea Bob.  I gotta run.  I'm done at work.

73,
Ellen - AF9J

[Tim WA1HnyLR]

Hi Ellen , Some months back you sent me an E mail RE: the Cheyenne. I wounder if you received it?Refer to my DX 60 mods in regard to to modulator section. A stock Cheyenne transmitter has somewhat better audio than the Icom 706, Yep, fingernails on blackboard. By reworking the modulator to a staight cathode follower design will deliver full modulation. You will see about 10-15 watts outpoot . This is the practical limit for power outpoot from a single 6146 that is screen modulated. The Cheyenne and other transmitter of this ilk make great exciters for a big linear amplifier. In regard to too much grid drive I have had the same issue with the one I have done up. I had to increase the values of screen dropping resistors for the driver stages. I observed plate color on one of the driver stages. This comes from improper engineering design and not a tube problem. Good luck with it. De Tim WA1HnyLR

[AF9J]

Hi Tim,

Yeah, I received the Cheyenne a few weeks ago.  As my first posting in this thread mentioned, I have a few issues.  First and foremost, I'm overhauling the power supply, since the cardboard tube electrolytics are basically shot (the no load HV B+ was only about 550V).  I'm just waiting for one of the capacitors, and the 100K resistors.  If they arrive today, I'll fix the power supply tonight.  I also have to check out the shunt resistor for the grid meter, to make sure that isn't the cause of my off-the-scale grid readings.  So, you're saying that Heath biased the drivers wrong - hmmm, I didn't know that.  That is  something to keep in mind.  Yeah, I may have to drive an amp, to get some more oomph.  the only thing is living in an aprtment, I can't run too much carrier, unless I want my neighbors up in arms (maybe 100W of carrierr is my practical limit).  I've also thought about getting a transmitter with bigger finals in it (I'm kind of limited spacewise, as to how much stuff I can have on my radio table {I'll post a picture I took a few days ago of it}).  I had a watch on a B&W 5100 in ePay (I think B&W 5100s are cool), but it turns out that the reason it's going so cheap, is that it's missing its entire modulator section (including the mod transformer).  So, I'm kind of hesitant to bid on a 5100, that's going dirt cheap, if it's going to cost me $50 to ship it, and I end up ahving to basically rebuild it from scratch.  Well, gotta run, work beckons.

73,
Ellen - AF9J