Warning: Creating default object from empty value in /homepages/11/d132647312/htdocs/Amfone/mkportal/include/SMF/smf_out.php on line 47
Scratchy Apache Mods




 
The AM Forum
July 09, 2020, 07:36:11 AM *
Welcome, Guest. Please login or register.

Login with username, password and session length
 
   Home   Help Calendar Links Staff List Gallery Login Register  
Pages: [1]   Go Down
  Print  
Author Topic: Scratchy Apache Mods  (Read 482 times)
0 Members and 1 Guest are viewing this topic.
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2199


Making AM GREAT Again!


« on: June 25, 2020, 06:59:25 PM »

Fixed an amplifier for a friend.  Upon getting ready to leave, he asks if I'd like an Apache!  Came with the HO10 scope as well.

Supposed to work, rectumfrier has been solid stated (with some wonderful age appropriate top hat style diodes lol..  Possibly selinium?) and supposedly caps where replaced...

I haven't opened up anything but the top cover, found a couple added switches.

Anyone have an idea of what they are for?

Mic jack was changed as well.

Overall, it's in clean shape.  No rust, two scratches on the side.  Make a good TX I suppose.

Any ideas on the switches?

--Shane
KD6VXI


* 20200625_152227.jpg (2542.83 KB, 4160x3120 - viewed 54 times.)

* 20200625_152216_HDR.jpg (3176.8 KB, 4160x3120 - viewed 68 times.)

* 20200624_185938.jpg (4215.35 KB, 4160x3120 - viewed 51 times.)
Logged
W1ITT
Member

Offline Offline

Posts: 374


« Reply #1 on: June 25, 2020, 07:25:34 PM »

Shane..  Don't overlook the HO-10 as it's a nice prize as well.  The fault that sends them to the sideline is that the HV transformer dies.  I ran one for years in the trapezoid mode to monitor linearity of various homebrew amplifiers until it crapped out.  It's small enough to fit in the equipment stacks, and it doesn't tie up a "good" scope for that function.  The Kenmore SM220 was about the same, but a bit higher quality.  I have seen a couple of those in use at BBC sites, cheap and cheerful and they do the trick.

73 de Norm W1ITT
Logged
Pete, WA2CWA
Moderator
Member

Offline Offline

Posts: 7760


CQ CQ CONTEST


WWW
« Reply #2 on: June 25, 2020, 07:34:36 PM »

I have both HO-10 and SM-220. I've used my HO-10 since 1964. I built it for Lafayette store demo when we were selling Heathkits. Still has all the original parts.  Smiley
The SM-220 is fine but CRT, and direct subs, are no longer available. Maybe, by this time, someone out there has figured out what to do about that.
Logged

Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
Pete, WA2CWA
Moderator
Member

Offline Offline

Posts: 7760


CQ CQ CONTEST


WWW
« Reply #3 on: June 25, 2020, 07:41:53 PM »

Supposed to work, rectumfrier has been solid stated (with some wonderful age appropriate top hat style diodes lol..  Possibly selinium?) and supposedly caps where replaced...
I haven't opened up anything but the top cover, found a couple added switches.

Any ideas on the switches?

--Shane
KD6VXI

Solid state silicon top hats were well into use by the late 60's. My 5R4's in my Apache (which I also built) are solid-stated with top hat rectifiers mounted on a perf board and glued in a cleaned out tube base and plugged into one of the 5R4 sockets. I even solid stated the low voltage section.
Based on the switch labeling, it looks like they have something to do with the audio. 6AL5 Clipper is still in its socket. There's a thousand and one audio mods out there on the web. Maybe your friend knows.
Logged

Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2199


Making AM GREAT Again!


« Reply #4 on: June 25, 2020, 08:46:44 PM »

Norm,

Yeah, it was the icing on the cake. All I had before was a rack mounted Tek mainframe scope.  This will look a lot better at the bedroom shack Wink

Pete, I figured they had an audio purpose.  The cut/through switch is just a pair of shielded audio cables.  The clip switch is switches in a 22k resistor between shielded audio cables.

Every tube is present sans the rectifier.

Guess I'll have to lug this lightweight out of its case.....

As to talking to the guy who gave it to me, he got it from an 11 meter operator who sold it because it didn't have 11 meters on the vfo.  The guy I got it from put it on a shelf (was a combo deal, he wanted the Johnson t-bolt and the multitude of Bird stuff that was in the lot).  The 11 meter op got it from an SK's wife.

Has the original build manual, but unfortunately no callsign in it.  My Viking II and other boat anchors all had a way to trace the original owners.  This one is a mystery.

--Shane
KD6VXI

Logged
DMOD
AC0OB - A Place where Thermionic Emitters Rule!
Contributing
Member
*
Offline Offline

Posts: 1502


« Reply #5 on: June 27, 2020, 12:55:20 PM »

I was given both a stock Apache and a Mohawk at a Hamfest. Someone mentioned my name at a Hamfest: "Phil will take it as he does the 'tube' thing!"  Grin

FWIW, here are the mods I applied to my Apache. 

Phil

* Apache Modificatiions for AMphone.pdf (335.53 KB - downloaded 24 times.)
Logged

Charlie Eppes: Dad would be so happy if we married a doctor.
Don Eppes: Yeah, well, Dad would be happy if I married someone with a pulse.NUMB3RS   Smiley
W2PFY
Contributing
Member
*
Offline Offline

Posts: 13165



« Reply #6 on: June 27, 2020, 08:04:37 PM »

I recall that about a month ago a ham with a 3 call came on to 3.885 and broke in with his recently resurrected Apache that was as stock from the factory with extremely distorted audio as it would have sounded back in the day. He met with scorn and immediately blasted with all the modifications that could be done to it to make it sound better. You know like cookie cutter hifi audio like most of us go for? He wasn't welcomed into the group, they did not turn it over to him again. He tried to get back into the fold but no one would have it. What a way to welcome a new AMer who thought he just did something great? OTOH, maybe he knew what he was getting into but it sure didn't sound that way to this listener?

I think he should fire it back up into a big ass linear  Grin Grin

ps: I never heard him on again?
Logged

The secrecy of my job prevents me from knowing what I am doing.
w4bfs
W4 Beans For Supper
Contributing
Member
*
Offline Offline

Posts: 1340


more inpoot often yields more outpoot


« Reply #7 on: June 27, 2020, 11:10:26 PM »

hi Shane .... looks like the switches are time era appropriate audio processing selects

a nice prize  Cheesy
Logged

Beefus

O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us.         Robert Burns
MikeKE0ZUinkcmo
Member

Offline Offline

Posts: 388



« Reply #8 on: June 28, 2020, 09:11:27 AM »

HO-10 was a standard accessory in the day, and Heath sold thousands of them and the ham band Pan adapter HO-13.  
Logged

Mike KE0ZU

Bold Text and PICS are usually links

https://mikeharrison.smugmug.com/
WD5JKO
Member

Offline Offline

Posts: 1854


WD5JKO


« Reply #9 on: June 28, 2020, 09:27:59 AM »


Shane,

   Perhaps you can revisit the Timtron Apache Turbo Modification:

http://amfone.net/Amforum/index.php?topic=24536.0
http://amfone.net/Amforum/index.php?topic=27820.msg212458#msg212458

My friend Nathan NR5P successfully pulled it off, but in that linked thread he had other issues going on.

Nathan made his Apache not only sound sweet, but had significant punch.

Jim
Wd5JKO

Logged
Jim, W5JO
Member

Offline Offline

Posts: 2459


« Reply #10 on: June 28, 2020, 10:43:50 AM »


Shane,

   Perhaps you can revisit the Timtron Apache Turbo Modification:

http://amfone.net/Amforum/index.php?topic=24536.0
http://amfone.net/Amforum/index.php?topic=27820.msg212458#msg212458

My friend Nathan NR5P successfully pulled it off, but in that linked thread he had other issues going on.

Nathan made his Apache not only sound sweet, but had significant punch.

Jim
Wd5JKO


Remember Lum, K5AYD 
Logged
KD6VXI
Contributing
Member
*
Offline Offline

Posts: 2199


Making AM GREAT Again!


« Reply #11 on: June 28, 2020, 10:56:37 AM »

Well, I plugged it in.

Every thing lit up, but I can't get current of any kind.

Tried spotting, no current.  Don't have a receiver where it's currently at, so guess time to drag one out.  For all I know, the meter could be toast.  Don't want to damage anything else, so it's gonna be a minute.

I did briefly flip to operate a d transmit, the red light over the operate switch didn't come on.


Tim's mods look like a winner.  I also wanna view Phil's on the pc.  Sometimes it's just too small on the phone..

Regardless, I think this tx is going to be a fixture here.  Even if that's inky because I don't want to lift it again LOL

--Shane
KD6VXI
Logged
Pete, WA2CWA
Moderator
Member

Offline Offline

Posts: 7760


CQ CQ CONTEST


WWW
« Reply #12 on: June 28, 2020, 02:19:37 PM »

There's a thousand and one mods are there for the Apache. Personally, if you use a decent microphone and  understand how to use and set the two audio controls (front panel and behind the key jack), the Apache can be made to run and sound great for many more years without a lot of mod diddling. I like to communicate with my rigs; I don't need to try and sound like a hi-fi station.
Logged

Pete, WA2CWA - "A Cluttered Desk is a Sign of Genius"
W4RFM
Member

Offline Offline

Posts: 347



WWW
« Reply #13 on: June 29, 2020, 12:15:02 PM »

Lets say I know a guy who in the 90's ran 30 minute music programming on an Apache around 6950, that had audio mods.  The entire front end of the audio was bypassed (not used) and line level -10 db audio was fed to the grid of the 12BY7 audio driver tube. That tube also had its cathode bypass changed out to a hifi component, probably 25 @ 25 or so. And it sounded wonderful.
Logged

BOB / W4RFM  "I have looked far and wide, (I also checked near and narrow)"
K0XP
Member

Offline Offline

Posts: 3


« Reply #14 on: July 03, 2020, 07:21:21 PM »

Actually, the transformer in HO-10s and HO-13s often doesn't die: instead, it's either the 1V2 or the caps, or one of the other possible HV troublespots within these scopes. The caps are easy to get and replace (one source, for $1.20 plus shipping for a 0.047 uF/2 kV and a 0.1 uF/1600 volter, is http://www.tuberadios.com/capacitors/ ; there are other vendors who charge as much as $4.95 just for the 0.1 uF cap alone  Shocked ). BTW, it is worthwhile to take the extra step required to replace both original 0.15 uF/1600 volt caps with at least 0.147 uF; it makes as much as 25% difference in the HV potential and you can see the reduction in hum at very low intensities on the scope.

The 1V2, however, can take some looking. I've replaced it with a pair of 1N4007s per filament winding leg on one of each of those models with success. When measured through 11M of resistance so as to limit the current through the meter to less than 100 microamps and thus load the circuit minimally, the HV should be at least -800V and can be as high as -1250V in a good unit. A decent tube tester will show the status of a 1V2 easily. I won't replace it with 4007s unless the 1V2 is bad and I can't find another for a decent price. Also, when I do put in 4007s, I connect a 1K resistor in series with the cathodes to limit the surge current drawn by the new capacitors (remember: this is a NEGATIVE supply, so the diodes must go in "backwards").

The intensity and focus pots in both units can be another troublespot; but I've managed to disassemble and clean up a number of these pots, then they work fine. Keep in mind that Heathkit, in their wisdom, allowed up to 600 volts on the terminals of that focus pot, a recipe for failure like few others.

The HO-13 has another HV troublespot of its own, too: there are two 12M resistors in series connected to the -HV to derive the negative bias required for the sweep oscillator's varactor (Rs 25 and 26, way over on the left edge of the schematic in the IF sweep oscillator dotted-line box). Those resistors can go either way: extremely higher, or extremely lower in value. Either way, they reduce the amount of sweep available from the IF sweep oscillator, and can also drag down the HV for the CRT (when they go much lower in value, the only thing protecting the varactor from overvoltage is that shunt 4700-ohm resistor!). Hooking as much as 600+ volts across a 1/2 watt resistor is a no-no (the -1200 HV is split between the two resistors); they're only rated at 350 volts at most and modern metal film types are often much less. I replace them with 4 or 6 resistors in series which makes for an unsightly mess but ensures they will last forever.

Finally, I ran across still another HV troublespot in one unit: the HV is routed to behind the 3RP1 CRT socket then soldered to pin 11 of the CRT. Then a 100K resistor is soldered between pins 11 and 2; that is, pin 11 is used as a tie-point for the 100K resistor (R75 on the HO-13 schematic). In this one unit, pin 11 was arcing to pin 10, right next door, which is supposed to be at a potential of about +90V; that is, there was almost 1200 volts between those two adjacent socket pins. (I finally saw this arc when I looked straight on at the socket with the lights off.) Pin 11 is supposedly not used inside the 3RP1, and in all but one HO-series scopes that I've worked on, there is no pin 11 on the CRT. But on this one particular unit, there WAS a pin in pin 11's place. I don't know whether this had anything to do with the arcing or not since supposedly, there is NO internal connection within the CRT on pin 11 (I've seen one tube pinout drawing, however, that showed pin 11 as "IC", meaning "Internal Connection"). In any case, now I routinely remove the HV wire from pin 11 and solder it directly to the 100K resistor (R75), then heavily insulate the bare junction with several layers of heatshrink and route the wire/resistor combo so they don't touch anything else. This avoids any other scope developing such an arc between these two scope pins. BTW, the arc was inside the two-layer bakelite socket and had burned through the outer wafer layer, and a PO had obviously attempted to "cure" it before by digging out the tracked bakelite.

SteveH K0XP
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

AMfone - Dedicated to Amplitude Modulation on the Amateur Radio Bands
 AMfone 2001-2015
Powered by SMF 1.1.21 | SMF © 2015, Simple Machines
Page created in 0.06 seconds with 18 queries.