Got-at Grundig 2065 dead/high HT... - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

paulsherwin · 6th Apr 2019, 10:08 am

The reservoir cap will charge to the peak voltage regardless of FW or HW rectification.

ms660 · 6th Apr 2019, 11:45 am

The greater the ripple voltage (eg: half wave versus full wave) the lower the HT will be.

Lawrence.

ekjdm14 · 14th Apr 2019, 1:05 pm

Right well, from some further "research" (i.e. Shango066 videos) I've gleaned some info, firstly it seems that at least in the US banging a diode across a selenium rectifier is an "acceptable method of repair" (read from, I believe, Howard Sams' literature) so I may be tempted to leave that for the moment.

And the power transformers seem to be a recurring weak-spot of this era Grundig kit.

Also, they tend to be high-hour sets (presumably due to how good they sounded) so no surprise the weak TX has already been replaced amongst other components (mine certainly is a high hour set judging from the dial lamp).

Final point gleaned, the selector switches are another weak point with age and can suffer carbon tracking, are a royal pig to sort and are best left alone unless they cause smoke! So for now I'll settle for the slightly off HT and when I get back on with this set I'll concentrate on why it seems to be silent except for some (normal/expected level) hum.

More to come on this when I find time, things are hectic at the moment with kids off school so high-voltage in the dining room is off the menu for now, 240VAC max!

Mike. Watterson · 14th Apr 2019, 4:34 pm

Quote:

Originally Posted by ekjdm14

Right well, from some further "research" (i.e. Shango066 videos) I've gleaned some info, firstly it seems that at least in the US banging a diode across a selenium rectifier is an "acceptable method of repair" (read from, I believe, Howard Sams' literature) so I may be tempted to leave that for the moment.

No, it's not! Bear in mind there are different constructions of rectifiers and USA is 110 to 120V.
Use the tag of the 1st electrolytic for 1N4007 rectifier or a suitable bridge, use heat shrink sleeve on Anode of rectifier and both wires of a series resistor rated at twice the wattage you think needed.
If a CT supply, then the resistor goes after the two rectifiers, or use two between them and transformer.

Old US service information or anecdotal US Forum comments are generally poor practice, especially on 220V to 245V.

paulsherwin · 14th Apr 2019, 7:25 pm

I agree with Mike.

ekjdm14 · 16th Apr 2019, 7:54 pm

Probably not the place to have mentioned it, given the safety/sanity aspect but please be assured that I did mean leave it for "the moment" in the most literal sense, just getting the actual fault ascertained/fixed before spending time tidying up someone else's work however good/bad it was. It will go, and will be done in a tidy/safe manner, just as long as the set can be made to work as it sits.

Still not in best of health for now but I will get there eventually!

6th Apr 2019, 10:08 am	#21
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Got-at Grundig 2065 dead/high HT... The reservoir cap will charge to the peak voltage regardless of FW or HW rectification.

6th Apr 2019, 11:45 am	#22
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Got-at Grundig 2065 dead/high HT... The greater the ripple voltage (eg: half wave versus full wave) the lower the HT will be. Lawrence.

14th Apr 2019, 1:05 pm	#23
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Got-at Grundig 2065 dead/high HT... Right well, from some further "research" (i.e. Shango066 videos) I've gleaned some info, firstly it seems that at least in the US banging a diode across a selenium rectifier is an "acceptable method of repair" (read from, I believe, Howard Sams' literature) so I may be tempted to leave that for the moment. And the power transformers seem to be a recurring weak-spot of this era Grundig kit. Also, they tend to be high-hour sets (presumably due to how good they sounded) so no surprise the weak TX has already been replaced amongst other components (mine certainly is a high hour set judging from the dial lamp). Final point gleaned, the selector switches are another weak point with age and can suffer carbon tracking, are a royal pig to sort and are best left alone unless they cause smoke! So for now I'll settle for the slightly off HT and when I get back on with this set I'll concentrate on why it seems to be silent except for some (normal/expected level) hum. More to come on this when I find time, things are hectic at the moment with kids off school so high-voltage in the dining room is off the menu for now, 240VAC max!

14th Apr 2019, 7:25 pm	#25
paulsherwin Moderator Join Date: Jun 2003 Location: Oxford, UK Posts: 27,970	Re: Got-at Grundig 2065 dead/high HT... I agree with Mike.

16th Apr 2019, 7:54 pm	#26
ekjdm14 Banned Join Date: Feb 2019 Location: Congleton, Cheshire, UK. Posts: 609	Re: Got-at Grundig 2065 dead/high HT... Probably not the place to have mentioned it, given the safety/sanity aspect but please be assured that I did mean leave it for "the moment" in the most literal sense, just getting the actual fault ascertained/fixed before spending time tidying up someone else's work however good/bad it was. It will go, and will be done in a tidy/safe manner, just as long as the set can be made to work as it sits. Still not in best of health for now but I will get there eventually!