Telequipment D61A low 13v supply line - UK Vintage Radio Repair and Restoration Discussion Forum

WaveyDipole · 4th Oct 2013, 3:59 pm

I've been checking the voltages of the supply lines (except the EHT lines) on the above scope which I recently acquired.

All of them are within tolenace except the 13v line where the voltage is slightly lower than the botttom limit:

-7.5v = 7.57v (-7.3v to -7.7v)
+7.5v = +7.72v (+7.1v to +7.9v)
-13v = -12.49v (-12.4v to -13.6v)
+13v = 11.87v (+11.9v to +12.1v)
+80v = 82.7v (+75v to +85v)
+110v = 112.1v (+107v to +117v)

I have the AC voltage selector set to the 234v setting. It was set to 214v by the previoous owner.

Is this anything to be concerned about? Might it be a factor in the triggering issues I am getting which are the subject of another thread?

I'm not quire sure how exactly this voltage is derived so precisely (is the 7.5v zenner involved perhaps?) but the source appears to be the Y amplifier circuit. Also why is it designated a 13v line, when, in fact, the expected voltage is actually around 12v - unless there is an error in the manual?

I've replaced the electrolytic caps for both the 13v and the 7.5v line to rule them out. I haven't touched the ones in the -7.5v line yet. The non-electrolytics look good as well.

The resistor values for R648, R651, R656, R657 and R665 seem to be pretty close to the correct value as well.

WME_bill · 6th Oct 2013, 3:30 pm

13V power rail. My copy of the D61A manual has a written note on p4/2, above the table of Supply Line voltages: " As the +13V is unregulated, it has been known for it to be as low as 11V without any adverse effect. This supply is generally around 12V. Above info obtained from Tek (Maidenhead) by phone." Note is undated, but I copied the manual late 1980's.
So I suggest you need not worry. wme_bill

WaveyDipole · 7th Oct 2013, 11:21 am

Bill, thanks for confirming that. I have also made a note on my copy of the manual.

4th Oct 2013, 3:59 pm	#1
WaveyDipole Nonode Join Date: Mar 2013 Location: Leicester, UK Posts: 2,535	Telequipment D61A low 13v supply line I've been checking the voltages of the supply lines (except the EHT lines) on the above scope which I recently acquired. All of them are within tolenace except the 13v line where the voltage is slightly lower than the botttom limit: -7.5v = 7.57v (-7.3v to -7.7v) +7.5v = +7.72v (+7.1v to +7.9v) -13v = -12.49v (-12.4v to -13.6v) +13v = 11.87v (+11.9v to +12.1v) +80v = 82.7v (+75v to +85v) +110v = 112.1v (+107v to +117v) I have the AC voltage selector set to the 234v setting. It was set to 214v by the previoous owner. Is this anything to be concerned about? Might it be a factor in the triggering issues I am getting which are the subject of another thread? I'm not quire sure how exactly this voltage is derived so precisely (is the 7.5v zenner involved perhaps?) but the source appears to be the Y amplifier circuit. Also why is it designated a 13v line, when, in fact, the expected voltage is actually around 12v - unless there is an error in the manual? I've replaced the electrolytic caps for both the 13v and the 7.5v line to rule them out. I haven't touched the ones in the -7.5v line yet. The non-electrolytics look good as well. The resistor values for R648, R651, R656, R657 and R665 seem to be pretty close to the correct value as well.

6th Oct 2013, 3:30 pm	#2
WME_bill Octode Join Date: Oct 2007 Location: Exeter, Devon, UK. Posts: 1,554	Re: Telequipment D61A low 13v supply line 13V power rail. My copy of the D61A manual has a written note on p4/2, above the table of Supply Line voltages: " As the +13V is unregulated, it has been known for it to be as low as 11V without any adverse effect. This supply is generally around 12V. Above info obtained from Tek (Maidenhead) by phone." Note is undated, but I copied the manual late 1980's. So I suggest you need not worry. wme_bill

7th Oct 2013, 11:21 am	#3
WaveyDipole Nonode Join Date: Mar 2013 Location: Leicester, UK Posts: 2,535	Re: Telequipment D61A low 13v supply line Bill, thanks for confirming that. I have also made a note on my copy of the manual.