AVO 215-L/2 AC/DC Breakdown Leakage and Isolation Tester - UK Vintage Radio Repair and Restoration Discussion Forum

trobbins · 13th Feb 2020, 11:27 am

I had enjoyed the restoration of a British Physical Labs RM215-L Tester 2 years ago (https://www.vintage-radio.net/forum/...d.php?t=149963), so was happy to take hold of a cheap AVO model to see what difference there was.

It's a bit chalk and cheese, as this AVO was made by Thorn EMI in Dover and is circa 1986, and in pristine condition along with HT probes you could trust.

No canned Hunt caps, but two tubular 15kV caps that I don't know the manufacturer - below photo of 5nF, and there is a 10nF 15kV (model 7006W).

2 nicely dipped transformers - the larger double-C core with 4.4kV and 6kV taps - but again no identifiable manufacturer.

A mini Zenith Model 33Y variac (240V 0.6A) for voltage adjustment.

A large PCB with opamps and ss parts, and six trimpots. Unfotunately I can't easily locate a service manual, so if anyone has a copy of an AVO RM215-L/2 I'd appreciate a hoy.

Ciao, Tim

short wave · 13th Feb 2020, 12:42 pm

Used one at Farnell (instruments at Wetherby ) in the 80s this is only the second one i ve ever seen! I presume there is a voltage doubler after the transformer. Nice find!

WME_bill · 16th Feb 2020, 1:34 pm

Avo RM215 insulation tester. (or BPL)
I attach the specification and circuit. All that I have, copied hurriedly one lunch hour 40 years ago.
This seems to be an update of the series of megohm meters made by British Physical Laboratories (BPL). I have information upon RM160, RM162, RM167 all 1956 to 1966 vintage with EF86 -ECC81 series, and RM175 with EF37A as the quasi- electrometer input valves instead of EF86. The RM215 is all semiconductor.
Your comment confirms that the firm was bought up by Avo, who continued with the same model.
wme_Bill

trobbins · 17th Feb 2020, 5:58 am

Top stuff Bill - that is the beast, and what I was looking for, as it gives me enough information to do some passive and then active testing.

Ed Dinning also said he has a full manual but didn't have a scanned copy, so I had a delayed backup plan

The earlier BPL version was a bit of a concern, not only for the probes/cables and internal mains AC wiring, but also the speaker output for ionisation indication is quite noisy due to neutral-earth noise. I had recently restored a portable 900VA isolation transformer (typically used for construction sites), which allows a local MEN to be used, but hadn't yet got the BPL out again to confirm that speaker noise was now subdued.

BPL had quite a range - I also have a RM175-LZ Mk2 megohmeter, and although cheap digital technology makes it easy to check up to 2 Gigaohm, this instrument can reach 5 Teraohm FS (not that I've been able to test it that far, as a 40kV 1000:1 probe only goes to 1 Gig).

Ciao, Tim

13th Feb 2020, 11:27 am	#1
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	AVO 215-L/2 AC/DC Breakdown Leakage and Isolation Tester I had enjoyed the restoration of a British Physical Labs RM215-L Tester 2 years ago (https://www.vintage-radio.net/forum/...d.php?t=149963), so was happy to take hold of a cheap AVO model to see what difference there was. It's a bit chalk and cheese, as this AVO was made by Thorn EMI in Dover and is circa 1986, and in pristine condition along with HT probes you could trust. No canned Hunt caps, but two tubular 15kV caps that I don't know the manufacturer - below photo of 5nF, and there is a 10nF 15kV (model 7006W). 2 nicely dipped transformers - the larger double-C core with 4.4kV and 6kV taps - but again no identifiable manufacturer. A mini Zenith Model 33Y variac (240V 0.6A) for voltage adjustment. A large PCB with opamps and ss parts, and six trimpots. Unfotunately I can't easily locate a service manual, so if anyone has a copy of an AVO RM215-L/2 I'd appreciate a hoy. Ciao, Tim Attached Thumbnails

13th Feb 2020, 12:42 pm	#2
short wave Pentode Join Date: Mar 2013 Location: Leeds, West Yorkshire, UK. Posts: 246	Re: AVO 215-L/2 AC/DC Breakdown Leakage and Isolation Tester Used one at Farnell (instruments at Wetherby ) in the 80s this is only the second one i ve ever seen! I presume there is a voltage doubler after the transformer. Nice find!

17th Feb 2020, 5:58 am	#4
trobbins Heptode Join Date: Oct 2009 Location: Melbourne Australia Posts: 901	Re: AVO 215-L/2 AC/DC Breakdown Leakage and Isolation Tester Top stuff Bill - that is the beast, and what I was looking for, as it gives me enough information to do some passive and then active testing. Ed Dinning also said he has a full manual but didn't have a scanned copy, so I had a delayed backup plan The earlier BPL version was a bit of a concern, not only for the probes/cables and internal mains AC wiring, but also the speaker output for ionisation indication is quite noisy due to neutral-earth noise. I had recently restored a portable 900VA isolation transformer (typically used for construction sites), which allows a local MEN to be used, but hadn't yet got the BPL out again to confirm that speaker noise was now subdued. BPL had quite a range - I also have a RM175-LZ Mk2 megohmeter, and although cheap digital technology makes it easy to check up to 2 Gigaohm, this instrument can reach 5 Teraohm FS (not that I've been able to test it that far, as a 40kV 1000:1 probe only goes to 1 Gig). Ciao, Tim