Eagle SA 100 My first tube amp!!
- Thread starter Eastham
- Start date
V helpful thank you!
Spent the last few hours of last night re-learning about valves, and with this diagram I'm quite hopeful that I'll get this bad boy working. Looking forward to the parts delivery! It's at times like this I miss Maplin...
Thanks again
Hi - found the original manual and guarantee card in parents loft... thought it might be useful.
I've cleaned one channel information up a bit too hopefully help readability.
Best
Alan
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OK, recapped and did a bit of spring cleaning of the SA-100 a few days ago, gave it a test drive and discovered one of the 6BQ5 tubes was kaputt. With that - and the 100 Ohm resistor I replaced that looked like a chip that had been caught in the basket of a chicken shop fryer for a week or so - maybe that's why it was in the loft in the first place...
I ordered two new JJ valves from the usual local online retailer, and they arrived this morning stuffed into a thin card envelope that looked like it had been used for a round of frisbee golf. Plugged them in, connected everything up and.... perhaps unsurprisingly one of them was moody, producing a low distorted sound when it warmed up.
So, they are being returned and I re-ordered. Cue sound of fingers tapping rhythmically on workbench.I'm positive the other valves in the amp need replacing too, but I'm going to check it's working reliably with these before investing any more time and money. I'm a bit surprised at (a) + how simple the design is and (b) - given this how much the costs in this little project are mounting up.
Any recommendations for good-sounding (by which I mean fairly transparent) valves at a reasonable price (by which I mean fairly cheap) for this little amp? A lot of the valves I've looked at seem to be targeted at guitar amps, and I'm a bit concerned celebrate valve "character" over sound quality and might make my Eagle amp sound like the music's being played the other side of a stud partition. On the other hand, this is a fairly humble amp and throwing 300+ quid's worth of Mullard valves in feels a bit like putting a Ferrari V8 in a Barn find MK1 Cortina with original brakes and gearbox.
P.S. Here's an improved SA-100 Circuit Diagram (fully tidied), and a PDF of the original manual minus the front picture.
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Dswankey
Lunatic Member
I'm assuming you're in either England or Europe based on using the term "valves"?
If so just a heads up to anyone offering suggestions that local US based options might not be cost effective for the poster.
Good point. I'm in London UK and hadn't written my email for an international audience! Apologies.
Dswankey
Lunatic Member
^ No worries, Just wanted you to get some region specific suggestions.
I hear you about NOS Mullards being very costly, for that matter Telefunkens & Amperex (Philips) too.
On another note nice amp!!! and here's hoping you get it back up and running with quality tubes that don't cost an arm and a leg.
Maybe @Hyperion will stop by and offer a suggestion off the top of my head I know he is based in England and might know of some Valve purveyors
I hear you about NOS Mullards being very costly, for that matter Telefunkens & Amperex (Philips) too.
On another note nice amp!!! and here's hoping you get it back up and running with quality tubes that don't cost an arm and a leg.
Maybe @Hyperion will stop by and offer a suggestion off the top of my head I know he is based in England and might know of some Valve purveyors
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trobbins
Super Member
6BQ5/EL84 are quite common in Australia as they were used in a few PA and magazine project amps, but I also note they were in my Ecko and Vox equipment, so maybe ask around on say vintage-radio.net as an alternative to trying to buy NOS from expensive dealers. At least you don't need matched pairs, so that may be a help in identifying locals that have 'pulled' valves (where one of a pair had gone bad but the other was still fine).
GREAT Diagram dont suppose you would have the voltages ?
Thank You Guys
maxhifi
Addicted Member
The 3-3 is direct coupled, so the grid of the EL84 is at 20 volts, and the cathode at 28. This puts the bias to 8 volts, which is right in range. SOME DAY I am going to have time to complete a 3-3.