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




 
The AM Forum
October 20, 2019, 08:10:12 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: Ranger Mods  (Read 11802 times)
0 Members and 1 Guest are viewing this topic.
W5SUM
Member

Offline Offline

Posts: 85


WWW
« on: July 02, 2005, 10:57:41 AM »

I have a Ranger here that I want to do the following mods on. Any help will be appreciated, I like to listen to others ideas.

Of Course, Add PTT using a good quality relay that not only handle the PTT but turn on the Red Led at the same time, and do any power supply switching that might be recommended.

Replace the OA2 in the VFO with a Zener

Ive already removed the 18K and put it inside the chassis and its rated
25 watts ( just cuz I had it )

Possibly replace the stock filter with a filter string and equalizing resistors or whatever

get rid of the tapped heat generating bleeder/divider resistor.

Increase the drive on 15 and 10

idea's fellows?

Ronnie - W5SUM
Logged

I got my Extra the old fashioned way, I earned it.
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10062



« Reply #1 on: July 02, 2005, 11:30:36 AM »

The bottleneck in audio response is the driver transformer.  It will perform much better if you take the DC off the primary.  Put a 1 mfd capacitor in series with the primary (doesn't matter whether it's inserted at the plate or B+ end of the winding).  Find a 30K 5 watt resistor, connect it to the paralleled plates of the driver stage, and return to the HIGH VOLTAGE B+ (the increased plate voltage will compensate for the voltage drop in the resistor).  The low frequency response and phase shift distortion should be improved, since the transformer is no  longer being saturated with DC.

When I had mine, I went a step further.  I removed the driver transformer, took it apart and removed the laminations, restacked the laminations like a power transformer (cross-laminated) by alternating the positions of the E and I sections of each adjacent  lamination.  Then I reassembled the transformer, and after I replaced it in the circuit I measured frequency response.  It was flat to well below 50~.

Note:  I am recalling this mod totally from memory of what I did some 30 years ago.  If there is not enough audio, measure the plate voltage on the parallel 12AU7 sections (or was that a 12AT7?).  If it is considerably below normal, try replacing the 30k resistor with a 10k.  I think I used a 30k, but it was possibly a 10k.  I recall using trial and error to determine the best value of plate resistor.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
KB2WIG
Contributing
Member
*
Online Online

Posts: 4317



« Reply #2 on: July 02, 2005, 11:59:08 AM »

ur right, its a 12AU7    klc
Logged

What? Me worry?
W1GFH
Guest
« Reply #3 on: July 02, 2005, 01:50:50 PM »

...thanks Don, I often wondered about rebuilding/replacing that driver xfmr. Wonder if there may be a drop-in replacement. Anyone know the stock driver xfmr specs?
Logged
ka0pad
Guest
« Reply #4 on: July 02, 2005, 02:33:57 PM »

I believe the P-T124E (Hammond 124E, ~25$) from AES is a drop in some people have used to improve the Johnson audio chain. Havnt gotten around to it myself so cant say if it's effective or not. The tubesandmore.com web page spec says 50hz-13khz, but the spec on the box of the one sitting here in front of me says 150hz-15khz???

Larry
Logged
k4kyv
Contributing Member
Don
Member

Offline Offline

Posts: 10062



« Reply #5 on: July 02, 2005, 04:20:08 PM »

Quote from: ka0pad
I believe the P-T124E (Hammond 124E, ~25$) from AES is a drop in some people have used to improve the Johnson audio chain. Havnt gotten around to it myself so cant say if it's effective or not. The tubesandmore.com web page spec says 50hz-13khz, but the spec on the box of the one sitting here in front of me says 150hz-15khz???


That's probably the spec with DC running through the primary.  The partial saturation of the core from the unbalanced DC effectively reduces the amount of iron in the transformer, and thus low end  response.  That's why most broadcast modulation transformers are designed for use with a reactor to take the unbalanced DC off the winding.
Logged

Don, K4KYV                                       AMI#5
Licensed since 1959 and not happy to be back on AM...    Never got off AM in the first place.

- - -
This message was typed using the DVORAK keyboard layout.
http://www.mwbrooks.com/dvorak
Steve W8TOW
Member

Offline Offline

Posts: 366



« Reply #6 on: August 09, 2005, 02:01:24 PM »

P-T124E is a VERY nice driver iron for both Valiants and Rangers (Viking s too)
I 've used these in several ...remember to install it "backwards"  in the circuit!!!

I've used it in a single ended driver stage with 12AU7 in parallel and also
PP 12AU7 ....frequently, I will block the DC in the single ended config tho....and
feed the Parallel 12AU7 via a series resistor....fyi
73 steve
8tow
Logged

Always buiilding & fixing stuff. Current station is a "Old Buzzard" KW, running a pair of Taylor T-200's modulated by Taylor 203Z's; Johnson 500 / SX-101A; Globe King 400B / BC-1004; and Finally, BC-610 with SX28  CU 160m morn & 75m wkends.
73  W8TOW
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 0.058 seconds with 18 queries.