Figuring out repairing Minstrel record player amplifier - UK Vintage Radio Repair and Restoration Discussion Forum

Kirtley2013 · 15th Dec 2019, 2:47 am

I picked up a simple record player today, Minstrel brand, I got it running, but I'm thinking I'll have to go through and give it a service.
The amplifier is very simple, 2 valves, but the smaller UY85 valve seems to be glowing very hot and bright, much brighter than the neighbouring UL84, I'd think its getting too much power to it, which put the resistor attached to it to suspicion, it runs and plays, but there was a suspicious smell after playing it for a couple of minutes, could that resistor be the suspect?, if so I'm struggling to identify it as the colour coding has seen some damage, its brown body, orange tip but the paint of the stripe or dot has flaked away, possibly was black.

Anyone able to help with it?

Station X · 15th Dec 2019, 11:52 am

Hello and welcome to the forums.

Rectifier valves and power resistors do get hot, it's just a question of how hot. The smell may be just be dust being burnt off.

It would be unusual to find a body-tip-spot resistor in a comparatively modern piece of kit like this. The one resistor I can see in you picture clearly has a three band colour code.

Have you tried measuring the resistors using a meter on ohms range so that you can eliminate them from your enquiries?

The circuit will be similar to that found in the Dansette Popular. Which has the same valve line up.

https://www.service-data.com/section.php/1521/1/a11115

ms660 · 15th Dec 2019, 12:04 pm

That resistor looks like the rectifier's surge limiter, body, tip, dot dog bone types are not unheard of in record players using those valves, the value typically being somewhere between 80 and 150 ohms, surge limiters can get hot during normal use, it might be worth measuring the voltage at the cathode of the rectifier.

If the body is brown and the tip is orange and there's no dot the resistor would be a 130 ohm job.

Lawrence.

Kirtley2013 · 15th Dec 2019, 5:47 pm

Thanks guys, I tested the resistor after managing to get my multimeter from the workshop, it was indeed 130 ohm and seems fine

The rectifier has about 260v across it, it could be that it's just the smell from the valves burning dust after sitting for many years and it may be running fine

Station X · 15th Dec 2019, 7:15 pm

The rectifier valve will only get excessively hot if called upon to supply excess current.

Given that this player has no audio coupling capacitor, the only likely cause of overheating is electrically leaking smoothing capacitors. If there's no mains hum and the smoothing can doesn't get excessively hot I wouldn't let it concern you.

If you check the DC voltage across the UL84's cathode resistor you'll be able to use Ohm's Law to calculate the combined anode and screen currents.

Ed_Dinning · 15th Dec 2019, 9:01 pm

Hi Kirtley, yes they are simple devices. If you have an autochanger that will give you more trouble than the amp as it needs to be very well cleaned of all the old concrete like grease.
Plenty of spares still available but be careful as it is, I think a live chassis model. It could be worth changing the ceramic coupling caps from the cartridge to the amp for modern class Y types.

Ed

15th Dec 2019, 2:47 am	#1
Kirtley2013 Triode Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne and Wear, UK. Posts: 12	Figuring out repairing Minstrel record player amplifier I picked up a simple record player today, Minstrel brand, I got it running, but I'm thinking I'll have to go through and give it a service. The amplifier is very simple, 2 valves, but the smaller UY85 valve seems to be glowing very hot and bright, much brighter than the neighbouring UL84, I'd think its getting too much power to it, which put the resistor attached to it to suspicion, it runs and plays, but there was a suspicious smell after playing it for a couple of minutes, could that resistor be the suspect?, if so I'm struggling to identify it as the colour coding has seen some damage, its brown body, orange tip but the paint of the stripe or dot has flaked away, possibly was black. Anyone able to help with it? Attached Thumbnails

15th Dec 2019, 11:52 am	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Figuring out repairing Minstrel record player amplifier Hello and welcome to the forums. Rectifier valves and power resistors do get hot, it's just a question of how hot. The smell may be just be dust being burnt off. It would be unusual to find a body-tip-spot resistor in a comparatively modern piece of kit like this. The one resistor I can see in you picture clearly has a three band colour code. Have you tried measuring the resistors using a meter on ohms range so that you can eliminate them from your enquiries? The circuit will be similar to that found in the Dansette Popular. Which has the same valve line up. https://www.service-data.com/section.php/1521/1/a11115 __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

15th Dec 2019, 12:04 pm	#3
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: Figuring out repairing Minstrel record player amplifier That resistor looks like the rectifier's surge limiter, body, tip, dot dog bone types are not unheard of in record players using those valves, the value typically being somewhere between 80 and 150 ohms, surge limiters can get hot during normal use, it might be worth measuring the voltage at the cathode of the rectifier. If the body is brown and the tip is orange and there's no dot the resistor would be a 130 ohm job. Lawrence. Last edited by ms660; 15th Dec 2019 at 12:32 pm. Reason: word change and additional info

15th Dec 2019, 5:47 pm	#4
Kirtley2013 Triode Join Date: Aug 2013 Location: Newcastle upon Tyne, Tyne and Wear, UK. Posts: 12	Re: Figuring out repairing Minstrel record player amplifier Thanks guys, I tested the resistor after managing to get my multimeter from the workshop, it was indeed 130 ohm and seems fine The rectifier has about 260v across it, it could be that it's just the smell from the valves burning dust after sitting for many years and it may be running fine

15th Dec 2019, 7:15 pm	#5
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Figuring out repairing Minstrel record player amplifier The rectifier valve will only get excessively hot if called upon to supply excess current. Given that this player has no audio coupling capacitor, the only likely cause of overheating is electrically leaking smoothing capacitors. If there's no mains hum and the smoothing can doesn't get excessively hot I wouldn't let it concern you. If you check the DC voltage across the UL84's cathode resistor you'll be able to use Ohm's Law to calculate the combined anode and screen currents. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

15th Dec 2019, 9:01 pm	#6
Ed_Dinning Dekatron Join Date: Jan 2004 Location: Newcastle upon Tyne, Tyne & Wear, UK. Posts: 8,195	Re: Figuring out repairing Minstrel record player amplifier Hi Kirtley, yes they are simple devices. If you have an autochanger that will give you more trouble than the amp as it needs to be very well cleaned of all the old concrete like grease. Plenty of spares still available but be careful as it is, I think a live chassis model. It could be worth changing the ceramic coupling caps from the cartridge to the amp for modern class Y types. Ed