Super Rocky

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Cressy Snr
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#106 Re: Super Rocky

Post by Cressy Snr »

Found the problem when dismantling. The transformer wires were terminated on tagboards and a loose piece of wire had somehow found its way between the 375 and 450V tags on the HT secondary, creating a short and destroying the transformer. It doesn’t take long does it :shock:
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#107 Re: Super Rocky

Post by JamesD »

No it doesn't - really sorry to read about your blown transformer - they really don't like short circuits on the windings!

I had a similar thing on my PT15 PP amp - I dropped a piece of copper wire across a psu capacitor and that blew up and melted the wire with a piece of copper wire dropping onto the tag strip holding the mains transformer secondaries that shorted and blew the transformer too. That scared me and got my valve amps banned from the house for a while... once I stopped shaking I felt like a real plonker... I was too embarrassed to talk about it at the time too... :oops: :oops: :oops:

Hope the replacement sounds as good!

ciao

James
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#108 Re: Super Rocky

Post by Cressy Snr »

Well, after a marathon session, which involved cutting out part of the ground busbar in order to be able to get at the tagboards holding the transformer wires, a load of desoldering, followed by a session of drilling, filing and bleeding, (and that was before the replacement transformer could even begin to be fitted) we now have a functioning amp.

I have back ache, neck ache and my eyeballs are on stalks, but I have music again.

I’m going to have my tea. There’ll be some booze later.
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Mike H
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#109 Re: Super Rocky

Post by Mike H »

Cressy Snr wrote: Wed May 27, 2020 6:42 pm I’ve got another mains TX and its already painted blue. First job’ll be to find out why the hell it burned. HT secondary is fused solid. TX is still too hot to touch.
My EL84 p-p TX also caught fire, not long after Ant made the wood cab for it, I guessed not enough air flow after that despite open mesh bottom panel and everything. Must be enamel got too hot and melted, shorting the HT sec. Didn't half stink! It was a Danbury. :shock:

I'm sure it was running on the verge of the total VA that was the main contributing factor, was just too bluddy hot.
 
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Mike H
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#110 Re: Super Rocky

Post by Mike H »

Cressy Snr wrote: Thu May 28, 2020 10:52 am Found the problem when dismantling. The transformer wires were terminated on tagboards and a loose piece of wire had somehow found its way between the 375 and 450V tags on the HT secondary, creating a short and destroying the transformer. It doesn’t take long does it :shock:
Sorry only just seen this (note to self, read to end of topic before replying!), mega bum, I've done that but "accidentally on purpose", was soldering up a PSU for a homemade 'scope, was using old tagged metal can elecs which are mounted in holes in the chassis plate with capacitor clips, and I was thinking why can't I parallel these two tags (there were three in total) and add the value of that section as well? Well because, that "free" solder tag wasn't a positive tag for another (unused) section, it was the earth tag! As yet not soldered! :shock: Cooked the TX immediately on switch on, was a real bummer cos I had bought that specially for the purpose from NOS while-stocks-last, and had been keeping it in reserve for quite a while so by this time couldn't be bought again!
 
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Cressy Snr
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#111 Re: Super Rocky

Post by Cressy Snr »

Mike H wrote: Thu May 28, 2020 6:45 pm Didn't half stink! It was a Danbury. :shock:
Yes, It has taken until now, to get that loathsome odour out of my nostrils. :lol:
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#112 Re: Super Rocky

Post by Cressy Snr »

Enjoying some lush piano toons with the repaired amplifier.

Weighs a ton with the bigger power transformer in the rear corner.
Installed another choke under the hood, whilst I was in there, so both power supplies are now LCLC

Power stage supply = 10H/50uF/320mH/50uF + 3.3uF MKP bypass.

Input stage power supply = 20H/100uF/320mH/100uF.

The 320mH chokes are Triad C40X 600mA jobbies.

It’s nice.
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Ray P
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#113 Re: Super Rocky

Post by Ray P »

Cressy Snr wrote: Thu May 28, 2020 10:25 pm Enjoying some lush piano toons with the repaired amplifier.
Pleased for you Steve. :thumbup:
Sorry, I couldn't resist!
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#114 Re: Super Rocky

Post by steve s »

Looks good Steve...
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#115 Re: Super Rocky

Post by Cressy Snr »

There’s a lot to be said for steam engine audio.

The NVA clone just wasn’t the same. To be fair, I would say it’s highly likely that there is a mismatch between my Fanes and powerful class B solid state. The speakers are so efficient that the NVA never really gets into its linear operating region. I mean, put the NVA clone on a pair of LS35As and it would beat the pants off my valve amp; horses for courses. I know Richard himself took part in a speaker/amp bake-off a few years ago, and positively hated his own amps through a pair of big 107dB horns, much preferring an Audion 300B SET on those speakers. This class B mismatch situation with high efficiency speakers, is probably why quite a few people on here sing the praises of high bias solid state, whether it be SE or PP. In most ways I’m still a beginner with this stuff and, much to my eternal embarrassment, I keep making the same feck-ups.

When you put a low power single ended valve amp with my speakers and compare it to a high power class B solid state. The fuzziness of the class B amp at the bottom of its operating range sticks out like a sore thumb in comparison. The class B amp was just so convenient and trouble free, unlike these bloody steam engine amps. Mind you; if I built them properly, got them right first time, then they’d work for years. :lol:
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pre65
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#116 Re: Super Rocky

Post by pre65 »

It's good to see you have Super Rocky back in action again.

I'm happy for you. :)
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ed
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#117 Re: Super Rocky

Post by ed »

Cressy Snr wrote: Fri May 29, 2020 11:00 am There’s a lot to be said for steam engine audio.

When you put a low power single ended valve amp with my speakers and compare it to a high power class B solid state. The fuzziness of the class B amp at the bottom of its operating range sticks out like a sore thumb in comparison. The class B amp was just so convenient and trouble free, unlike these bloody steam engine amps. Mind you; if I built them properly, got them right first time, then they’d work for years. :lol:
not sure why I'm posting this, but......

I'm not sure of the point when comparing low power single ended valve with high power class b solid state....it really does seem like apples and oranges. The only possible conclusion could be preference under any given circumstance.

to my mind a much more telling comparison would be a low powered single ended valve against a low powered single ended mosfet..this one still has me confused after 15 years. The latter is convenient and has proven trouble free.

just sayin

edit: but don't misunderstand me Steve, there's no way I'm defending an NVA against a Rocky..that's one step beyond.
Last edited by ed on Fri May 29, 2020 12:02 pm, edited 1 time in total.
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Nick
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#118 Re: Super Rocky

Post by Nick »

The speakers are so efficient that the NVA never really gets into its linear operating region.
The thing is, if its not linear at low level, it will never stop being non linear at low level no matter how big a signal is passed through it as there will always be point as the signal passes through zero and looks like a low level signal. Thats sort of the problem with class B
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#119 Re: Super Rocky

Post by Cressy Snr »

ed wrote: Fri May 29, 2020 11:46 am
not sure why I'm posting this, but......

I'm not sure of the point when comparing low power single ended valve with high power class b solid state....it really does seem like apples and oranges. The only possible conclusion could be preference under any given circumstance.

to my mind a much more telling comparison would be a low powered single ended valve against a low powered single ended mosfet..this one still has me confused after 15 years. The latter is convenient and has proven trouble free.

just sayin..
That’s what I’m sort of getting at. Low power single ended solid state and efficient speakers, is probably a much fairer comparison, than a high power class B amp on efficient speakers, but I’m not explaining myself very well.
Just trying to articulate what I heard the other night when I put the the clone on in place of the smoking wreck that had been the Rocky. I normally stay up a couple of hours listening at night. But only managed twenty minutes with the clone, before I got bored and went to bed. Maybe my expectations have been changed.
Nick wrote: Fri May 29, 2020 11:47 am The thing is, if its not linear at low level, it will never stop being non linear at low level no matter how big a signal is passed through it as there will always be point as the signal passes through zero and looks like a low level signal. Thats sort of the problem with class B.
Thanks Nick. Not as simple as I thought. As per. :)
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#120 Re: Super Rocky

Post by Nick »

Of course the measured distortion goes down as the low level part becomes a small percentage of the entire signal and is the small signal is riding on a larger signal then it will be kept away from the 0v point, but the large signal itself still has to pass through the 0v higher distortion point. I look forward to hearing the MOFO amp when the madness if over for this reason.
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