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Magnum Deltaforce Power Output

B

Beakster

Member
May 27, 2008
14
8
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Hi,

I've got an old Magnum Deltaforce I got used about a decade ago. Recently hooked it up to a power meter (Daiwa) to see what it's putting out. Seems to be quite a bit lower than spec. Also when I turn the power knob only the first 50% seems to do anything. From 50% to 100% there's no change, e.g. I get maximum power at 50% of power setting and nothing more after. I wonder if this could mean one of the dual finals are dead?

On AM I get 7 watts, regardless of what I set the mic gain to or if I'm talking/whistling or silent.
On FM and Sideband I get 12-13 Watts max (when whistling with mic gain up).

Manual says:
FM is 30W Max
SSB is 30W Peak
AM is 8W average, 30W Peak

I'm not looking to get big power out of this radio, I'm planning to get an amplifier so less than these power ratings are more than enough to drive it. But if something is broken or not working correctly I'd like to fix it. The lack of change from 50% power to 100% makes me think something might be up. Is it possible for only one final to blow and would that create this kind of a situation?

Any advice appreciated.
Thanks
 

Yes that is low for power. What kind of meter are you using? Do you have another radio you can compare on the meter?
 
I was given a deltaforce once about 10 years ago. Turned out to be a basket case. Even magnum couldnt fix it so it qas sold on ebunk for parts. Hmmm...
 
Even though I only had my deltaforce for a few weeks I liked it and if I get a chance to grab another I probably would.
I found an old email from a forum I posted in. It was 2015 and I was living in Wa state east side, Pend Oreille county and acquired the rig for nothing and found out why.
According to my post the mods to the radio were botched and it took out the cpu. Now its coming back to me. The rusty steel door creeks open hahaha!
Magnum is in Wa state but their service tech was in California if I remember correctly.
 
Thanks. I've tried the adjustments but still not seeing more than about 15w, half what it claims.

Also still confused by the lack of change in power when the control knob goes from 50 to 100%.

What's the best way to check if one of the finals isn't performing correctly? Seems like it could be a culprit if I'm getting exactly half of what the specs claim.
 
Beakster said:
I've got an old Magnum Deltaforce I got used about a decade ago
Click to expand...

May need all electrolytic capacitors replaced? Might be where I would start. That and checking bias current to the driver and finals?

Since you got it used about a decade ago, there is a real possibility that both of your finals are weak. In my experience, power output slowly drops over time instead of completely quits altogether as long as there was no catastrophic failure. (I.e. bias set way too high, regulator failure/shorted etc.)

Only so much juice in the lemon!(y)

73
David
 
Thanks, sounds like a bit of an overhaul is in order. I'll look at doing a bit at a time. Is there a write up anywhere on how to best check the bias into the finals?

Also, I'm not currently using a dummy load, just measuring power into my antenna. Would the power meter show reduced power as a result of the SWR? Could it be that if I use a dummy load I'll see the full power?

Thanks
 
http://www.cbtricks.com/radios/rflimited/delforce/graphics/deltaforce_main_sch.pdf

http://www.cbtricks.com/radios/rflimited/delforce/graphics/deltaforce_omegaforce_alignment.pdf

See the 2 links above.

Variable Resistor Adjustment
RV-101 AM "S" Meter
RV-102 SSB "S" Meter
RV-103 SSB Squelch
RV-104 AM Squelch
RV-106 FM Deviation
RV-107 SSB Carrier Balance
RV-108 Transmit Frequency Adjustment
RV-109 FM Repeater Tone
RV-111 RF Meter
RV-112 Q169 Final Bias Control
RV-113 Q168 Final Bias Control
RV-114 Driver Bias Control
RV-116 SSB ALC
RV-117 AM Carrier Low Power Adjustment
RV-118 AM Carrier high Power Adjustment
RV-119 AM AMC
RV-120 CW Side Tone

73
David
 
The Delta Force is my favorite all time radio, still have one. On most radio's the RF power control is not an exact numerical control. So 25, 50, or 75 % will not be exact. If yours has been sitting it might need to have the controls cleaned and some things adjusted.

Your watt meter is the biggest variable, might not be a true peak reading meter. Did you use a dummy load or through an antenna? What voltage are you running the radio at? All these things make a difference.

If your getting good reports I bet she is still kicking and doing fine. You can expect 30 honest peak watts from that radio, an extra 5-8 more watts will not make a difference so don't try to wrangle every last watt out.

I think mine has a dead key range of 1-7 watts. On SSB it peaks at 30-34 watts on a Bird 43p meter. FM is set from like 3-20 watts since things get hot fast in this mode. I talk mostly SSB these days so I run it at maybe 10-14 watts PEP and then let my amp do the work.

Hope this helps, take care.
 
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Hi, so things are looking better with the Deltaforce. It seems I did have a power supply problem. My PSU has a 240/120V switch on it. It had been so long since I used it I forgot that the last time was when I took it back to Scotland, so it was still on 240V. Now I'm using it in Canada this was causing it not to deliver enough DC under load. Testing showed it dropped down from 13.8V to 12V on transmit.

Now I've got the PSU set to 120V I get a solid 13.8V even when transmitting. This has also raised the power output to 25 Watts on FM.

So looks like I could tune the power output for a bit higher, but it's not recommend. I'll do an alignment based on information above when I get a chance. I also found a couple of amazing videos on youtube that show how to diagnose issues and align the finals correctly on the Deltaforce:




I think it's a good point about the finals on this radio getting tired. I see that genuine 2SC1969s are no longer available. Seems the best options are either HC or Eleflow copies.

I just got an RM KL-203p amp which I've got it hooked up to so now I'm able to put out 100W and a new Sirio Gainmaster just arrived. Now I just need some propogations :D
 
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That's good news. The After market 1969 finals might actually do less watts then what you have now. I would leave it and just run it on low into your amp. The RM 203 amps can get warm fast and they don't like to be over driven. I would add a small fan on the heat sink of that amp just to be safe. Should be a great combo.
 
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