We seek to understand and document all radio transmissions, legal and otherwise, as part of the radio listening hobby. We do not encourage any radio operations contrary to regulations. Always consult with the appropriate authorities if you have questions concerning what is permissable in your locale.

Author Topic: ICOM AD-55 power supply output voltage adjustment  (Read 217 times)

Offline alpard

  • Full Member
  • ***
  • Posts: 172
  • Karma: +6/-9
    • View Profile
ICOM AD-55 power supply output voltage adjustment
« on: October 14, 2020, 1808 UTC »
Hi All

I checked my ICOM AD-55 output voltage, and it is 20V.
This is too abnormally high voltage I thought.

Is there ways to lower the voltage on the AD-55?

« Last Edit: October 15, 2020, 2236 UTC by alpard »

Offline ThaDood

  • Hero Member
  • *****
  • Posts: 605
  • Karma: +9/-2
  • There
    • View Profile
    • Extreme Part #15!
    • Email
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #1 on: October 14, 2020, 1851 UTC »
Wow... Somethin' ain't right there. Well, open that up and look for, either an adjustment POT, or for cold solder joints by a Zener Diode, or an LM78##-like Voltage Regulator. Just for the heck of it, have you put it to a load, like a 12VDC light bulb, and measured the voltage under load? Not having that power supply myself, I'm just speculating, but hopefully enough to help.
I can't decide upon what's worst, young and stupid, or old and chemically dumbed down.

Offline alpard

  • Full Member
  • ***
  • Posts: 172
  • Karma: +6/-9
    • View Profile
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #2 on: October 14, 2020, 1937 UTC »
 I will open up the AD-55E, and see if I could see the voltage adjustment pot.
« Last Edit: October 15, 2020, 2237 UTC by alpard »

Offline alpard

  • Full Member
  • ***
  • Posts: 172
  • Karma: +6/-9
    • View Profile
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #3 on: October 14, 2020, 2051 UTC »
Wow... Somethin' ain't right there. Well, open that up and look for, either an adjustment POT, or for cold solder joints by a Zener Diode, or an LM78##-like Voltage Regulator. Just for the heck of it, have you put it to a load, like a 12VDC light bulb, and measured the voltage under load? Not having that power supply myself, I'm just speculating, but hopefully enough to help.

Thank you for your advice.  I have opened up the AD-55E, and there was no pot to adjust the voltage. 

« Last Edit: October 15, 2020, 2232 UTC by alpard »

Offline ChrisSmolinski

  • Administrator
  • Marconi Class DXer
  • *****
  • Posts: 26410
  • Karma: +63/-45
  • Westminster, MD USA
    • View Profile
    • Black Cat Systems
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #4 on: October 14, 2020, 2141 UTC »
Did you measure the AD-55 voltage under a load?
Chris Smolinski
Westminster, MD
eQSLs appreciated! csmolinski@blackcatsystems.com
netSDR / AFE822x / AirSpy HF+ / KiwiSDR / 900 ft Horz skyloop / 500 ft NE beverage / 250 ft V Beam / 58 ft T2FD / 120 ft T2FD / 300 ft south beverage / 43m, 20m, 10m  dipoles / Crossed Parallel Loop / Discone in a tree

Offline alpard

  • Full Member
  • ***
  • Posts: 172
  • Karma: +6/-9
    • View Profile
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #5 on: October 14, 2020, 2309 UTC »
No, haven't done it yet.  I wouldn't imagine the output voltage from the AD-55 would drop a lot under the load. Would you?
« Last Edit: October 15, 2020, 2233 UTC by alpard »

Offline Stretchyman

  • Hero Member
  • *****
  • Posts: 509
  • Karma: +21/-35
    • View Profile
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #6 on: October 15, 2020, 0853 UTC »
A schematic would be useful!

However if it's a simple pass transistor linear jobbie then the smoothing cap may be shot and passing A.C. ripple, just a guess.

Put your meter on A.C. see anything? If you do it's the cap.

Str.
'It's better to give than receive' so why RX when you can TX!

                            Buy one from me, NOW!

Great discounts on ALL my transmitters if purchased via HFUnderground


                                              ;)

Offline alpard

  • Full Member
  • ***
  • Posts: 172
  • Karma: +6/-9
    • View Profile
Re: ICOM AD-55 power supply output voltage adjustment
« Reply #7 on: October 15, 2020, 1511 UTC »
Great idea on reading AC from the output DC. If the smoothing cap is bad or diodes are bad, then it will show
solid AC voltage readings.  Will try that.

I don't have the schematic, and couldn't find it anywhere.
« Last Edit: October 15, 2020, 2235 UTC by alpard »