Vintage PA Grampian type UA ENSA - Page 2 - UK Vintage Radio Repair and Restoration Discussion Forum

maninashed · 26th Feb 2012, 10:52 pm

It states on the circuit diagram that the amp has a 12watt output, but I think that may be a little optimistic! There is no o/p spec relative to the input sensitivity.
Bill

Neil Purling · 27th Feb 2012, 8:55 am

I was wondering about the input sensitivity.
Grampian would have to quote it for their products. How else would you be able to choose the right microphone, or check a gramophone had the right pickup.
After you restore this, you would like to have a use for it.

That ceramic former the dropper resistance is on......... It has spiral grooves to keep the turns separated?
Were the wires always bare, or should they be hidden under another layer of ceramic to insulate them?
Is rewinding (with suitable resistance wire) an option if you cannot get a fixed resistor of the correct value?

maninashed · 27th Feb 2012, 11:21 am

The amp is descibed as 12watt on the cct diagram, but I think that may be a little on the optimistic side. I dont know what the sensitivity is for full output yet and wont do until its working again, but that is definitely the original mike, so I presume its designed for that level of input. Someone may have the specs of the mic, maybe they could help out. Still looking for that elusive big dropper.
Bill

julie_m · 27th Feb 2012, 4:05 pm

12 watts isn't unreasonable, as the two output valves are rated for 9W each.

There are forum members who have the ability to wind custom transformers, which would take care of the potential safety issue and the dropper at a stroke. Might be worth asking in "sets and parts wanted".

dseymo1 · 27th Feb 2012, 6:01 pm

Being an ENSA model, this was probably designed to meet specifications provided by the Association, rather than the other way round, so chances are that they were never published as such.

26th Feb 2012, 10:52 pm	#21
maninashed Rest in Peace Join Date: May 2011 Location: Preston, Lancashire UK Posts: 955	Re: Vintage PA Grampian type UA ENSA It states on the circuit diagram that the amp has a 12watt output, but I think that may be a little optimistic! There is no o/p spec relative to the input sensitivity. Bill

27th Feb 2012, 8:55 am	#22
Neil Purling Nonode Join Date: Jul 2005 Location: Hull, East Yorkshire, UK. Posts: 2,087	Re: Vintage PA Grampian type UA ENSA I was wondering about the input sensitivity. Grampian would have to quote it for their products. How else would you be able to choose the right microphone, or check a gramophone had the right pickup. After you restore this, you would like to have a use for it. That ceramic former the dropper resistance is on......... It has spiral grooves to keep the turns separated? Were the wires always bare, or should they be hidden under another layer of ceramic to insulate them? Is rewinding (with suitable resistance wire) an option if you cannot get a fixed resistor of the correct value?

27th Feb 2012, 11:21 am	#23
maninashed Rest in Peace Join Date: May 2011 Location: Preston, Lancashire UK Posts: 955	Re: Vintage PA Grampian type UA ENSA The amp is descibed as 12watt on the cct diagram, but I think that may be a little on the optimistic side. I dont know what the sensitivity is for full output yet and wont do until its working again, but that is definitely the original mike, so I presume its designed for that level of input. Someone may have the specs of the mic, maybe they could help out. Still looking for that elusive big dropper. Bill

27th Feb 2012, 4:05 pm	#24
julie_m Dekatron Join Date: May 2008 Location: Derby, UK. Posts: 7,735	Re: Vintage PA Grampian type UA ENSA 12 watts isn't unreasonable, as the two output valves are rated for 9W each. There are forum members who have the ability to wind custom transformers, which would take care of the potential safety issue and the dropper at a stroke. Might be worth asking in "sets and parts wanted". __________________ If I have seen further than others, it is because I was standing on a pile of failed experiments.

27th Feb 2012, 6:01 pm	#25
dseymo1 Retired Dormant Member Join Date: Dec 2007 Location: Shropshire, UK. Posts: 3,051	Re: Vintage PA Grampian type UA ENSA Being an ENSA model, this was probably designed to meet specifications provided by the Association, rather than the other way round, so chances are that they were never published as such.