pye 76f

[AlanBeckett]

rob,

B8A bases are getting a bit thin on the ground. I have a few second hand ones if you're stuck. There are some Chinese ones on eBay but without skirts, and some in Italy which are clearly B7Gs.

Alan

[tiv48]

thanks alan i have a few scrap chassis but i am loathe to use used valve bases ,its a lot of work to fit one and then find it has loose connectond ect .as i say i will try and get the set working first.
rob t

[Bushbaby]

Do you mean like this?

Regards

Rob

   

[AlanBeckett]

Rob,

They look like Octals

Alan

[pwdrive]

I thought the EL41 had a glass pip locator?

Lawrence.

[tiv48]

well i have had time to do a bit more today.decided to plug in via lamp limiter.ht rose to 310 volts with slight hum from speaker ht checked at output tx.
some thing wrong as ht should be 235 volts!.
next check was R37 on alans circuit it was of coase o/c.
i did not have a 1k5 wire wound so fitted a 1k8.
power on again ,better this time ht 250 volts and some life from the speaker .
swiched to mw band and stations picked up at least at the low end of the band.
tried lw radio 4 and one other recived.
sw and trawler bands dead.
one other thing audio output not what it should be quality not bad .
if volume wound past 3/4 output goes unstable.
i am not shore the rs output tx is conected correctly.
i have not as yet tested any of the valves and the speaker i am useing is 6 ohms.
so a lot more work to be done .
rob t

[tiv48]

ok wave change switch cleaned with servisol .now working on all bands.
alighnment checked nearly spot on (can't believe it had not bee got at.
checked el84 and ebc41 by substitution ,el84 ok ebc41 gave more volume.
rechecked the wireing to the output tx found that the wires to the hum cancel and ht were the wrong way round!.
the output stage no longer goes unstable and sound is good quality.
the volume is still on the low side with the cathode of the el84 at about 4.5 volts instead of 6.5 volts the cathode resistor measures 182 ohms.
i still think the output tx is to blame i dont think its up to it.
rob t
pic of tx before wires swaped

[AlanBeckett]

rob,

Are A, B, C and D the outout taps?
If so you could try different ones ie change the ratio.

Alan

[tiv48]

hi alan i think so..the black wire on the primary is now on pin3 .
the first thing i will try is connecting the sets own speaker the one i am useing is a 70 watt 85db hifi speaker.
i am not shore if the rs tx was made for this type of circuit.
but will try the secondry taps
rob t

[AlanBeckett]

rob,

Ah, so. The hifi Speaker may well be pretty inefficient comapred with its own one.

Alan