I have spent several hours today trying to work out more clearly where the problem is, but for some reason this time the reverb did not cut out for any length of time so I was not able to establish whether there was still a signal into the reverb tank when it is inaudible.
However, having taken off the rear grill and reading your previous email again I am suspicious that the 12AT7 is in the wrong place.
Looking at the amp from behind and starting at the left end there is a large transformer which logically is the power supply as it's very near the mains power socket.
To the immediate right of that is an RCA jack which I believe is the reverb send (it has the red RCA plug in it which connects to the left RCA jack on the reverb tank, currently via the extra reverb control box to reduce the send level as much as possible and minimise audible distortion on clean settings).
To the immediate right of that RCA jack is a small valve. This is currently a 12AX7 (make uncertain). To the immediate right of that is another 12AX7 (SOVTEK). They are both partially obscured by the two leftmost output valves (both SOVTEK 5881/6L6) which are nearer the back edge of the chassis.
Further along to the right of those two valves is a bit of a gap and then the RCA jack for what I believe is the reverb return (a black RCA plug connected to the right side of the reverb tank). To the immediate right of that is another 12AX7 (SOVTEK). In front of them are two more output valves marked HARMA 5881.
Still moving to the right is what I reckon to be the output transformer.
In the space between that transformer and the right hand end of the chassis are two more small valves: a Philips 12AT7 and an Electro-Harmonix 12AX7. To emphasise - the 12AT7 you mentioned in your email is located almost in line with the MIDI In socket on the back face of the chassis.
So neither tube near what I think is the reverb send is a 12AT7 - they are both 12AX7 and the 12AT7 is way down the other end at the right.
Can you please confirm whether the positioning of the valves that I've described is correct? I would kinda' help if there was a diagram of what should go where in the PDF manual...
Thanks and regards,
PS I'm still keen to know the in's and out's of sending the chassis back to you for an upgrade.
I sure would like to know if the right valves are in the right place.
Subject: Trying a second re-send of my 18 Mar email re: Valve positioning affecting Superfly Combo reverb problem?
Date: 1 April 2007 18:42:00 BST
To: email@example.com, firstname.lastname@example.org
Perhaps someone reads your "info" mailbox more often?
I'm still hoping for a reply to my email. I've scoured the Web for just a simple list or diagram of which tube goes where with no luck.
I was confused because looking at the valves in the amp, the 12AT7 did not appear to be in the right place. It should be the small valve right next to the red RCA plug in the attached picture I think!, but there was a 12AX7 there. Although I'd got a PDF of the Superfly user guide, for some reason it did not include a simple diagram of the valve placement.
(Strangely, although the Zinky website Q&A archive included a detailed statement on the necessity of using only matched, high-quality valves, I noticed that the power valves were made up of different makes! Presumably they were put in by a previous owner, not as supplied by Zinky - at least at that time they worked fine.)
Not being terribly familiar with spring reverbs, I wasn't 100% sure which was the input and which was the output. So I emailed Bruce back to ask for a simple run-down of where the valves should go, in a straightforward left-to-right order.
I also reminded him about my earlier question regarding shipping.
Again, getting no response in the next week, I re-sent the email (below right).
That had no effect so I had another go on 1 April, targeting an additional address from the Zinky web site. I was to hear nothing from Mr Zinky for the rest of that year and I decided at that point that because I was missing so much information, and the problem was limited to an intermittent reverb, I would live with it for the present.
That is not the end of the story of course - it picks up again in part 12.