Search found 46 matches

by RJKflyer
Tue Mar 26, 2024 3:18 am
Forum: Amplifiers
Topic: MV-55 output issues
Replies: 14
Views: 3586

Re: MV-55 output issues

They're neither 'small' nor 'glass'!

They're ceramic, industrial, high voltage (600V) High Breaking Capacity (10,000A) fuses.
by RJKflyer
Mon Mar 25, 2024 3:06 pm
Forum: Amplifiers
Topic: MV-55 output issues
Replies: 14
Views: 3586

Re: MV-55 output issues

The MV-55 was specified with Bussmann BBS-3/4 (i.e. 750mA fast blow).

An alternative is the Littelfuse BLS.750 - same rating and behaviour.

They're both 0.406" dia. by 1.375" long.
by RJKflyer
Mon Mar 18, 2024 8:33 am
Forum: Amplifiers
Topic: Cap Upgrade: DIY
Replies: 14
Views: 2784

Re: Cap Upgrade: DIY

Looking at the Prem 12 schematic, my immediate choices for caps to upgrade would be: 1. The 0µ15 600V in each grid of the 6550s 2. The 1µ 400V with 0µ15 400V bypass in the 6FQ7 grids to ground These are arguably the 'most' audible. I would suggest Solen FEP (Tin/PTFE). In my MV-55 I did the No.1 cap...
by RJKflyer
Tue Mar 12, 2024 3:27 pm
Forum: Preamps
Topic: Tubes for PV10al
Replies: 5
Views: 118

Re: Tubes for PV10al

Agree fully re matching, and note that this means both sections as well as both tubes. Remember you have no balance control... I've had my PV-10AL for 20 years and it remains a fine-sounding preamp. The only 'bad' tubes have been brand new chinese tubes - I've had several failures, poor performers, ...
by RJKflyer
Wed Feb 14, 2024 7:41 am
Forum: Preamps
Topic: PV-12 help needed
Replies: 17
Views: 1878

Re: PV-12 help needed

Subjectively: those resistors are life-expired. Replace. Objectively: you've done well measuring the temps. Assuming correct, the burnt pair (which you've confirmed are approximately the same value to the lesser damaged ones) are some 7˚C hotter, which assuming an ambient of about 20˚C is about 20% ...
by RJKflyer
Sat Feb 10, 2024 11:15 am
Forum: CJO Feedback, Suggestions and Report Site Problems
Topic: Cannot find member details
Replies: 4
Views: 243

Re: Cannot find member details

Very odd. I am now able to, after temporarily pausing, then re-enabling, my VPN connection.

I wonder if the original VPN connection was possibly showing up as a 'blacklisted' one?

Anyway, sorry for the excursion, clearly an issue at my end.
by RJKflyer
Fri Feb 09, 2024 2:30 pm
Forum: CJO Feedback, Suggestions and Report Site Problems
Topic: Cannot find member details
Replies: 4
Views: 243

Cannot find member details

If I click on a member name, I get routed to an error page.

"Not Acceptable

An appropriate representation of the requested resource /memberlist.php could not be found on this server."
by RJKflyer
Fri Feb 09, 2024 2:22 pm
Forum: Amplifiers
Topic: MV-55 - most significant improvement yet
Replies: 2
Views: 127

MV-55 - most significant improvement yet

My MV-55 sprang a hum, which was traced to a failed heater rectifier, or possibly a dry joint on one due to the heat. I took the opportunity to do some replacements and upgrades: 1. Replaced heater rectifiers with Vishay SBYV28-100-E3/54 which are faster and softer recovery, plus lower dissipation -...
by RJKflyer
Fri Feb 09, 2024 7:29 am
Forum: General Discussion - CJ related topics
Topic: MV-55 anyone with experience of this?
Replies: 5
Views: 4147

Re: MV-55 anyone with experience of this?

Let me post a separate thread on that.
by RJKflyer
Fri Feb 09, 2024 4:05 am
Forum: General Discussion - CJ related topics
Topic: MV-55 anyone with experience of this?
Replies: 5
Views: 4147

Re: MV-55 anyone with experience of this?

(Sorry - bit late to this conversation but only just spotted it). Having owned a MV-55 for nearly 30 years I can attest to it being a very sweet performer, and so much so that this month I chose to perform a few minor upgrades to assure its future. in terms of what I have observed, accepting I am bu...
by RJKflyer
Thu Feb 08, 2024 7:22 am
Forum: Preamps
Topic: PV-10B - the 'zener board' - was this ever reverse engineered?
Replies: 0
Views: 166

PV-10B - the 'zener board' - was this ever reverse engineered?

Anyone?

I'd be really interested to learn of the circuitry, purpose and any other details.
by RJKflyer
Sun Feb 04, 2024 5:22 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

I buy only best quality caps for all HV and instrumentation work and they are randomly labelled - they tumble down the production line and the print ends up where it ends up. These days, with semiconductor circuits a bit less susceptible to pickup due to lower impedance maybe, a general lack of AC r...
by RJKflyer
Sun Feb 04, 2024 4:01 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

Yes, you may well be right.

It does emphasise that as modders we need to get this right when we install them, else large sums of money may well end up making the equipment far worse.
by RJKflyer
Sun Feb 04, 2024 3:38 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

The lesser Solen PPE FC polypropylene range do not purport to be marked for polarity, and my experience is that they are truly random. The vastly expensive FEP Tin/Teflon ones were stated on my supplier's website as: "S3Q series have the outer foil on the right of the marking. The Outer foil en...
by RJKflyer
Sun Feb 04, 2024 12:16 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

No contact required: (a) as I get close to the cap you see noise increase, and (b) it's insulated!

It's a metal can which acts as an aerial. Although harder to see you may be able to spot that the residual noise level is higher with the 'backwards' cap.
by RJKflyer
Sun Feb 04, 2024 9:46 am
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

I thought this practical test might be informative, and hopefully persuasive for anyone who considers orientation unimportant. I have knocked together a simple 12AU7 two-stage cathode-follower amplifier with about 20dB of gain, running at 200V plate. First video shows the input capacitor (which coup...
by RJKflyer
Sat Feb 03, 2024 2:08 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

An alternative is with your 'scope.

See with red end to the 'scope sense connection (red croc clip) we have outer foil 'exposed' and it picks up the 50Hz in my case.

With red end to black croc clip ('scope gnd) we are now 'shielding' the red input and it picks up almost nothing.
by RJKflyer
Sat Feb 03, 2024 2:04 pm
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

I use a bespoke foil side tester - proprietary design to Mr. Carlson's Lab on Patreon. This unit is a very sensitive amplifier with a front end that electronically switches the two capacitor connections between input and gnd in the sensing amplifier. LED bar graph indicates the received 'noise' whic...
by RJKflyer
Sat Feb 03, 2024 10:20 am
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

Re: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

It is not about the 'polarity' of the capacitor - it is about its behaviour as an aerial. Nearly all film (or foil) caps are essentially a rolled up number of alternate sheets of dielectric and metal foil, or a metallised dielectric. The foil or metallised layers are the 'plates' of the cap. The lea...
by RJKflyer
Sat Feb 03, 2024 9:05 am
Forum: DIY, mods, tweaks
Topic: WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors
Replies: 14
Views: 1297

WARNING: incorrectly labelled, but EXPENSIVE, V-Cap and Solen PTFE capacitors

I have just replaced the output tube grid signal caps, and the ground return caps in each channel in my MV-55, with Solen FPE (Tin/PTFE) and V-Cap ODAM respectively. I do a lot of valve equipment restoration and test every film cap before installation as I am used to minimising noise in high-impedan...