Ekco A239/1: A Sorry Tale.

[Joe]

I've looked at this several times in the months since my last post but cannot find where the devil the fault is. I can't SEE anything touching anything it shouldn't. As Steve says, wave switches are the root of all evil but there's no sign of tracking there.

The other problem now is that I've pinched a couple of it's valves. One of these was the ECC85 which did indeed prove to be well past its best.

One for Sir Sydney methinks.

The data is here https://skydrive.live.com/redir.aspx?cid...4e6cdebd02&resid=132B7A4E6CDEBD02!196&parid=root The /1 version is covered from page 9 onwards.

- Joe

[Steve_P]

First, the HT does go through the wavechange switch, but it does not have to. Actually, it's better for the ECC85 if it doesn't and is always there. SW3C on the Ecko diagram - take it out and join all three wires together. Insulate them and switch on. It now won't track HT on the control because there won't be any!

As far as the chassis shocks go, C64, C65 and R36 would be possible here. This set is AC only so the chassis earth is linked to transformer Ov by R36 and C65. The chassis is earthed and so is the mains transformer. If the mains transformer is leaking to earth then it can have this effect. So it may be the transformer. Try isolating it with paxolin and non-metallic screws. It's not ideal, but it'll 'get you home' as it were.

The DM70 is driven off the HT from the Screen Grid of V5. It might be worth replacing C72 as well as checking C43, C76, C26.

Good luck here. I've got another Ekco on a shelf here which does something similar. Tinkerbell always puts it close to me, I wonder what she's trying to say?

Cheers,

Steve P.

[Joe]

Thanks, Steve, I'll investigate and report back.

- Joe

[Steve_P]

Don't blow yourself up...

Cheers,

Steve P.

[Joe]

Just to be clear, the 300VDC is only on the Gram socket when the wave switch is in the Gram position.

Don't worry about me - I'm well practised at keeping my fingers out of the way. Blowing equipment up is a different matter though.

- Joe

[Joe]

I've just started to have a look and I think you've consulted the wrong diagram, Steve. The /1 version has an EM80, not a DM70. The first thing I'll do is megger the transformer.

- Joe

[Joe]

Right, all three windings of the power transformer megger out absolutely fine as does C64. R36 is fine and I'd previously changed C65.

Tackling the switch put the willies up me far more than the prospect of getting a couple of hundred volts up my arm so I proceeded slightly differently to instructed by breaking the circuit here - blue line:-

   

There's still 250VDC on the gram socket - it'll be down a bit as it's currently got a weak EZ80.

I'll keep looking.

- Joe

[Joe]

I've now discovered, still with the HT line broken as shown in the previous post, that there's HT on the slider of the Tone pot whatever position the wave switch is in. Turning the knob varies the amount - zero at either end and over 200V when it's in the middle.

C54, C55 and C56 are all fine, the latter two being new ones.

I KNOW I'm missing something obvious but can't see or think what.

- Joe

[Steve_P]

Have you measured each winding on the Transformer to Chassis? Maybe it's leaking to earth that way. Break the HT between T1 and R28, then check for HT at the tone control.

Change the screened cables, C60, C59, C55.

Cheers,

Steve P.

[Mark R]

C58, 59 and 60 on the manufactures sheet and associated resistors?

then 62 and 63?

cheers Mark