Ambassador 545H - UK Vintage Radio Repair and Restoration Discussion Forum

Gabe001 · 27th Sep 2020, 5:49 pm

Hello, just a quick question on an ambassador 545h I'm currently working on. It was sold to me as "sort of working" but I didn't power it up myself yet.

The set has been got at, but it looks ok. The grid coupling capacitor which should be 0.02 microfarads was replaced with a 0.05 one (silver one with plastic sleeving). I think the 0.0005 microfarad capacitor running from one end of the grid coupling capacitor to ground is missing. Can anyone spot it?

If it is missing, was this done intentionally?

Pictures for reference. I'm ready to start replacing the wax capacitors, just making sure I'm not missing something obvious first.

Thanks

Gabriel

cathoderay57 · 27th Sep 2020, 9:19 pm

The 0.0005uF appears to be the IF filter cap. If the lower valveholder in the image is that of V4, there is a brown slab (silver mica) capacitor to the right of the valve holder, which might be it. There would be no reason to remove it, since I've never known one fail. The grid coupler value is OK so long as it is't leaking. Cheers, Jerry

Gabe001 · 27th Sep 2020, 10:23 pm

Hi Jerry, thanks for replying. The brown micas n the picture are c16 and c17 (0.0001 and 0.0002) top left corner of circuit diagram, not the elusive 0.0005 unfortunately.

The Strad pw461 I've done a couple of months back interestingly doesn't have a 0.0005 in that location, just the resistor. It uses exactly the same valve line-up.

cathoderay57 · 28th Sep 2020, 8:25 am

My mistake. The 0.0005 isn't an IF filter, it's a treble cut tone filter. Since the treble response of most radios of this period is relatively feeble you can happily do without it, unless you particularly like a "mellow bellow" tone. Cheers, Jerry

Gabe001 · 28th Sep 2020, 9:23 am

Ok brilliant Jerry, thanks. I'll leave it out then.

Gabe001 · 3rd Oct 2020, 4:19 pm

Jerry I've finished the ambassador, decided to leave the 0.0005 capacitor out. It sounds good without it and is a really great performer, nice rich sound and good reception

cathoderay57 · 3rd Oct 2020, 4:59 pm

Hi Gabriel, nice work. I've never come across any Ambassador sets. The same 4-volt valve line-up is often found in Murphy sets of the 1940s. There is an interesting picture of an Ambassador 548 on Page 178 Of "Radio! Radio!" by Jonathan Hill. That model incorporates the receiver into a bookcase with solid walnut shelves, from 1948. Made by R.N. Fitton Ltd., Hutchinson Lane, Brighouse, Yorks.

Gabe001 · 3rd Oct 2020, 5:12 pm

Same line up as the Strad I've got in my kitchen, but it performs quite a bit better imo. Or maybe I am getting a bit better at restoring them, the Strad was my first project.

27th Sep 2020, 5:49 pm	#1
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,642	Ambassador 545H Hello, just a quick question on an ambassador 545h I'm currently working on. It was sold to me as "sort of working" but I didn't power it up myself yet. The set has been got at, but it looks ok. The grid coupling capacitor which should be 0.02 microfarads was replaced with a 0.05 one (silver one with plastic sleeving). I think the 0.0005 microfarad capacitor running from one end of the grid coupling capacitor to ground is missing. Can anyone spot it? If it is missing, was this done intentionally? Pictures for reference. I'm ready to start replacing the wax capacitors, just making sure I'm not missing something obvious first. Thanks Gabriel Attached Thumbnails

27th Sep 2020, 9:19 pm	#2
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Ambassador 545H The 0.0005uF appears to be the IF filter cap. If the lower valveholder in the image is that of V4, there is a brown slab (silver mica) capacitor to the right of the valve holder, which might be it. There would be no reason to remove it, since I've never known one fail. The grid coupler value is OK so long as it is't leaking. Cheers, Jerry

27th Sep 2020, 10:23 pm	#3
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,642	Re: Ambassador 545H Hi Jerry, thanks for replying. The brown micas n the picture are c16 and c17 (0.0001 and 0.0002) top left corner of circuit diagram, not the elusive 0.0005 unfortunately. The Strad pw461 I've done a couple of months back interestingly doesn't have a 0.0005 in that location, just the resistor. It uses exactly the same valve line-up.

28th Sep 2020, 8:25 am	#4
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Ambassador 545H My mistake. The 0.0005 isn't an IF filter, it's a treble cut tone filter. Since the treble response of most radios of this period is relatively feeble you can happily do without it, unless you particularly like a "mellow bellow" tone. Cheers, Jerry

28th Sep 2020, 9:23 am	#5
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,642	Re: Ambassador 545H Ok brilliant Jerry, thanks. I'll leave it out then.

3rd Oct 2020, 4:19 pm	#6
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,642	Re: Ambassador 545H Jerry I've finished the ambassador, decided to leave the 0.0005 capacitor out. It sounds good without it and is a really great performer, nice rich sound and good reception

3rd Oct 2020, 4:59 pm	#7
cathoderay57 Nonode Join Date: Oct 2017 Location: Bristol, UK. Posts: 2,384	Re: Ambassador 545H Hi Gabriel, nice work. I've never come across any Ambassador sets. The same 4-volt valve line-up is often found in Murphy sets of the 1940s. There is an interesting picture of an Ambassador 548 on Page 178 Of "Radio! Radio!" by Jonathan Hill. That model incorporates the receiver into a bookcase with solid walnut shelves, from 1948. Made by R.N. Fitton Ltd., Hutchinson Lane, Brighouse, Yorks.

3rd Oct 2020, 5:12 pm	#8
Gabe001 Octode Join Date: Oct 2019 Location: Stockport, Greater Manchester, UK. Posts: 1,642	Re: Ambassador 545H Same line up as the Strad I've got in my kitchen, but it performs quite a bit better imo. Or maybe I am getting a bit better at restoring them, the Strad was my first project.