Kenwood TS700G question - UK Vintage Radio Repair and Restoration Discussion Forum

axels121 · 20th Oct 2008, 11:39 pm

hi

i have a ts-700g, which is giving a mains hum on transmit. has anybody any solutions for this problem? (i only run it on mains)

Sean Williams · 21st Oct 2008, 4:05 am

Try a different power unit?

We really need much more information from you before you can get a decent answer - what power supply are you using? are you using the radio barefoot (no external amplifier)... It is using the original microphone?, is your antenna correctly installed?.......

Cheers
Sean
M1ECY

Valleyjinker · 21st Oct 2008, 2:50 pm

In what mode of transmission are you getting the hum? Is it on FM? Is your microphone wiring in good condition? Can you try a differrent mic? Can you listen to your own transmission on another radio? If so try removing the mic and using the standby-send switch top put the radio in TX do you still get the hum?

Do you have the radio near a large source of AC magnetic field - eg another power supply or a computer monitor? If so try moving it away.

Can you try the radio on a car battery or other 12 volt power source?

HamishBoxer · 21st Oct 2008, 6:32 pm

The TS700G has a built in power supply,not separate.

Trish · 21st Oct 2008, 9:58 pm

I don't know this rig... I would suspect that the power supply main electrolytic capacitor(s) might have dried up with age..

The problem will show itself up as hum on transmit first, as the PSU is loaded up... If the rig allows you to reduce the power level on transmit. Turn down the power and if the hum reduces or goes away. Then I would bet that the capacitors have had it..

Trish

Valleyjinker · 22nd Oct 2008, 11:23 am

Quote:

Originally Posted by HamishBoxer

The TS700G has a built in power supply,not separate.

Yes, it does, and a wierd one too.

It contains a DC/DC converter that steps up the 13.8 volts to 20 volts. It needs the converter because it is capable of working from an external 13.8 volt source. Those converters were the most unreliable part of the set.

If you try the set on an external supply at least the 13.8 volt part of the internal psu can be eliminated as a source of the problem.

axels121 · 22nd Oct 2008, 10:41 pm

many thanks for answers if this helps the ts-700g is mains run in that mode on tx there is a mains hum wile when run on dc 12v there is no hum on tx

Sean Williams · 23rd Oct 2008, 4:49 am

there you go - the internal PSU is in need of some new capacitors - the old ones will have dried out internally!

Trish · 12th Nov 2008, 4:54 am

I'm wondering if you managed to find the problem axels121 it would be nice to know..

Trish

axels121 · 12th Nov 2008, 11:21 pm

Yes it was the caps. Had dried out with age now running on mains and 12 volt 100%. Thanks to all who answered with help.

20th Oct 2008, 11:39 pm	#1
axels121 Retired Dormant Member Join Date: Oct 2008 Location: co armagh northern ireland Posts: 3	Kenwood TS700G question hi i have a ts-700g, which is giving a mains hum on transmit. has anybody any solutions for this problem? (i only run it on mains)

21st Oct 2008, 4:05 am	#2
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: ts-700g question Try a different power unit? We really need much more information from you before you can get a decent answer - what power supply are you using? are you using the radio barefoot (no external amplifier)... It is using the original microphone?, is your antenna correctly installed?....... Cheers Sean M1ECY __________________ Engineers make things work and have spare bits when finished

21st Oct 2008, 2:50 pm	#3
Valleyjinker Retired Dormant Member Join Date: Oct 2006 Location: Nottingham Posts: 35	Re: ts-700g question In what mode of transmission are you getting the hum? Is it on FM? Is your microphone wiring in good condition? Can you try a differrent mic? Can you listen to your own transmission on another radio? If so try removing the mic and using the standby-send switch top put the radio in TX do you still get the hum? Do you have the radio near a large source of AC magnetic field - eg another power supply or a computer monitor? If so try moving it away. Can you try the radio on a car battery or other 12 volt power source?

21st Oct 2008, 6:32 pm	#4
HamishBoxer Dekatron Join Date: Aug 2007 Location: W.Butterwick, near Doncaster UK. Posts: 8,935	Re: Kenwood TS700G question The TS700G has a built in power supply,not separate.

21st Oct 2008, 9:58 pm	#5
Trish Retired Dormant Member Join Date: Apr 2005 Location: Reading, Berkshire, UK. Posts: 95	Re: Kenwood TS700G question I don't know this rig... I would suspect that the power supply main electrolytic capacitor(s) might have dried up with age.. The problem will show itself up as hum on transmit first, as the PSU is loaded up... If the rig allows you to reduce the power level on transmit. Turn down the power and if the hum reduces or goes away. Then I would bet that the capacitors have had it.. Trish

22nd Oct 2008, 10:41 pm	#7
axels121 Retired Dormant Member Join Date: Oct 2008 Location: co armagh northern ireland Posts: 3	Re: Kenwood TS700G question many thanks for answers if this helps the ts-700g is mains run in that mode on tx there is a mains hum wile when run on dc 12v there is no hum on tx

23rd Oct 2008, 4:49 am	#8
Sean Williams Dekatron Join Date: Feb 2005 Location: St.Ippolyts, Hitchin, Hertfordshire QRA IO91UW Posts: 3,518	Re: Kenwood TS700G question there you go - the internal PSU is in need of some new capacitors - the old ones will have dried out internally! __________________ Engineers make things work and have spare bits when finished

12th Nov 2008, 4:54 am	#9
Trish Retired Dormant Member Join Date: Apr 2005 Location: Reading, Berkshire, UK. Posts: 95	Re: Kenwood TS700G question I'm wondering if you managed to find the problem axels121 it would be nice to know.. Trish

12th Nov 2008, 11:21 pm	#10
axels121 Retired Dormant Member Join Date: Oct 2008 Location: co armagh northern ireland Posts: 3	Re: Kenwood TS700G question Yes it was the caps. Had dried out with age now running on mains and 12 volt 100%. Thanks to all who answered with help.