The AM Forum

I want to turbo my ranger.
Does the increased filament current draw of the 6550 an issue ??
I dont want to burn up my power transformer.

They used an oversize fil supply because of the acc socket on the back for running outboard gear like the 6N2 transmitter and vfo.  Look in the manual and you will see the rating you are allowed to pull from the acc socket. its more then the 6550s will pull.

The 6550's draw 1.6 amps each vs. .9 for the 6L6, 1614, 7027A etc.  So about 10 watts more. If you eliminate the two rectifier tubes it should be about a wash in total transformer draw if you are drawing more mod resting current or trying to run more output power then that might be an issue. I notice my Ranger power transformer gets quite warm just running the filaments for a long time. All of the powers add up. So if you are drawing 100 ma more on the 600 volt line it is 60 watts more load on the power transformer.

I thought about KT88's which are very similar to 6550's (same filament current) but I think I will use 7027A's as I have them and I also think that the dinky mod transformer in the Ranger is also more of a bottleneck than the output tubes. I haven't figured out yet what "turbo" your Ranger really means.  If the mod tubes and transformer in there do not fully modulate to your liking then why not throttle the power back a little. No one would ever notice 10 watts less. It is a fraction of a dB (60 > 50 watts = -.8 dB)  

To me Turbo'ing the Ranger is making it more modern with respect to power consumption and reliability.

Dont overlook the Silvania 8417 tube. Its a hot shot.  70 watts out for a pair in Ultra linear mode Class Ab1.   It has more than double the amplification factor of a pair of 6550s.  At 550 volts if you go the current, They make 100 watts a pair!

They plug right in, Pull less fil current than the 6550s.  I ran a pair in my ranger and got great results.   

Little pricey These days but you might have some or just dont mind the 50 to 75 bucks a pair.

C

I think some radio guys are as nuts as the audiophiles. I can't imagine why you would want 70 watts of audio for a 60 watt transmitter not to mention the fact that the modulation transformer or any that would reasonably fit in there would not handle that power.

Do these guys also use monster cable to connect there microphone? Hey I have a question - how come we don't have ultra linear modulation transformers?

Anyhow I forgot to mention that if you remove the vacuum tube rectifiers and go solid-state you will probably need to lower the line voltage if yours runs high. One way to at least get a little help is to use the unused 5V winding from removing the 5R4 to buck the primary thus lowering the input by 5 volts.

I use the filament voltage as a reference. With all the tubes installed I set the line voltage so that the filament voltage is at or within 5% minus of 6.3 V. On my Ranger this works out to be about 112-113 volts at the transformer or about 117-118 line volts. Then your high voltages are reasonable. A little more than with the tubes but not way out there.

All kinds of good info here. I think Franken-Ranger is a more descriptive term than Turbo-Ranger.

I installed a large variac on my operating & work benches and keep the voltage at 115.

I like the idea of measuring filament voltage to set the variac.

Yeah for sure.. Variac is the way to go over trying to use a fil winding like that.  Get a good one and run the boat anchor gear off it if you feel it will help.

Keep in mind the Johnson Spec is 105 to 120 volts AC.   You would only need to act when the rig is outside this range by a good margin.   Here, I have 126 most of the time and that is outside my comfort zone on some rigs. 

C

My experience in dropping in the 6550s in the Ranger modulator, is that the tubes want to draw a lot more current than the 1614s of course, and I had to increase the bias voltage on the tubes to calm them down. Its nice to have those tubes loaf along with lots of reserve/headroom if you want to use them.

I would consider having the stock mod transformer rewound by someone like Gary WZ1M, who does a great job. The stock Ranger mod transformer is centre tapped to allow you do drive a higher power ie. class B modulator as in the Desk Kilpwatt. I know the transformer has its limitations otherwise.

I had some issues with ultrasonics noted in the audio from the stock inverse feedback setup in the Ranger, from that tertiary winding on the mod iron. I had to change the values of components in the circuit to eliminate the feedback.

Al VE3AJM

Keep in mind that 105 to 120 is about a 15% range which would translate to just about a 100 volt range on the HV. Quite a difference.

Just emailed WZ1M Thanks for the tip. My mod trans smoked because of a bias supply failure.
I was going to install an old NIB Stancor but if I can get the origonal rewound. I would like that better.

I am thinking of building a line voltage monitor using filament transformer and set my BA variac so the meter reads 6.3 volts off of the filament Xfmr.

Using a filament transformer to monitor is no different than just measuring the line itself. It just follows the line. It is an OK way to do it as long as your meter has enough resolution at that voltage. My purpose of using the filament within the Ranger is that I can correlate it to a specific line voltage. In my case 112 or so equaled 6.3 volts. Once I know that then I can set the line voltage to that value and know that I am at the proper filament voltage. You wouldn't be able to directly correlate this using a stand-alone transformer. The filament voltage is brought out to the back panel octal socket so you could measure it there when it is installed in the cabinet if you like. Its a shame Johnson did not have a HV measurement position on the front panel meter. It would be easy to add if you were willing to give up one of the existing measurements or change the switch to one that had an additional position.

I run a large bucking transformer ar each bench to get 108-113V at the various RX, TX, and accessories.
Small 3A 12V are used for various comm or wood cabinet radios upstairs.

The reduction in heat is very very noticable which results in longer life for all components, especially marginal transformers and filter caps.

Carl