Shaftesbury 519 amplifier

[Guitarist28]

I hope you can see these ok?

Lawrence, how loud is your amplifier in realistic terms? Given the size of the output transformer I wouldn't expect it to be earth shattering (my Matamp Little Rock, handwired with just one 6V6 make the house shake by comparison and its rated at 4 watts!). Perhaps I'm expecting too much from this little guy?

[ms660]

Originally Posted by Guitarist28

Lawrence, how loud is your amplifier in realistic terms?

Very deaf because I don't own one....The reverse engineered schematic I did was from your photo's and some others on the web....

We need to see or know what valve pins are connected to what in the EF86/tremelo circuit in order to reverse engineer a schematic of that section....

Lawrence.

[Guitarist28]

Thank you Lawrence and apologies as mixed you with another forum member.
Best regards

[Herald1360]

A small output transformer won't make the amp significantly quieter but it will have less bass response- probably not something much needed for other than a bass guitar anyway.

[Station X]

Originally Posted by Guitarist28

the EF86 has either blown or is not getting power as there is no filament glow

There are two main reasons why valves don't light up and you've mentioned both of them.

Check for power (AC Volts) on the heater pins of the valve holder.

Unplug the valve and measure the resistance between its heater pins.

If both tests pass, the chances are you have a bad connection within the valve holder. You may need to clean the valve pins and/or nip up the sockets.

http://www.r-type.org/exhib/abn0041.htm

[ms660]

Thanks to Robs' photo's I've managed to come up with a first attempt for a circuit for the tremolo section, in basic terms it looks like a standard phase shift oscillator.

After I washed my specs I also did a revised schematic for the main section of the amplifier, also shown below.

Guilty as charged if there's any errors.

Lawrence.

[Guitarist28]

Many thanks Lawerence, its very much appreciated. I will have a look tomorrow and any errors wont be on your part but mine for not providing sufficient info!

[Guitarist28]

I'm beginning to wonder if this is the same amp??

https://www.youtube.com/watch?v=6UzFW0dPF5E

[Edward Huggins]

At a Post #168, and still counting, this Thread seems to be getting a bit over extended.
This is nothing more than a simple, single-ended, EL84, 4.5 watt amplifier.
Something is definately wrong, irrespective of the rather basic Tremulo circuit - possibly in the way the voltages have been measured. In the meantime have the (very few) valves yet been tested?

[ms660]

Originally Posted by Guitarist28

I'm beginning to wonder if this is the same amp??

https://www.youtube.com/watch?v=6UzFW0dPF5E

I reckon so or very close.

Nice SG.

Lawrence.

[ms660]

Originally Posted by Edward Huggins

At a Post #168, and still counting, this Thread seems to be getting a bit over extended.
This is nothing more than a simple, single-ended, EL84, 4.5 watt amplifier.
Something is definately wrong, irrespective of the rather basic Tremulo circuit - possibly in the way the voltages have been measured. In the meantime have the (very few) valves yet been tested?

So far as I'm aware, Rob has no electronics background.....we should communicate with him in a manner and pace that suits, if that means reams of pages on the forum then that's what it will be, at least he's making an effort and as a result we now have a better understanding of what's in the amplifier which is more than can be said before he started this thread...

Lawrence.

[Guitarist28]

I don’t wish to cause issues to anyone. I’m a semi retired analytical chemist/construction HSE director/adviser having recently returned from a nuclear build project in Wales (I can’t say any more on this). My electronics knowledge is in the lowly side hence coming on this forum for much valued and much appreciated help/ guidance.

I shall test the valves on my Avo mk1 VCM but would think that they are all working.

[ms660]

Originally Posted by Guitarist28

Many thanks Lawerence, its very much appreciated. I will have a look tomorrow and any errors wont be on your part but mine for not providing sufficient info!

I didn't wash my specs enough....the anode load resistors for the ECC83 in your amp are I think 120k and not 220k as I have shown in the schematic I did, I will post up a
2nd revision version later on.

Lawrence.

[ms660]

2nd revision.

Lawrence.

[Guitarist28]

Lawrence
Your drawings do appear correct (and thank you again) and I shall add in the missing values to the relevant components and upload the amended schematics.
I have tested the valves and they do appear to be in tolerance.
The EF86 is working as the tremolo section will only work when switched on, the oscillation can be heard with the volume is turned right up .
Now it has more volume (I'm still not convinced it 100% yet), I'm thinking it is going to sound bright even with a 1000pF coupling cap. Perhaps I am expecting a lot from the Richard Allan speaker?
I have learnt so much out of this little project so far and it definitely nearing completion now.

Best Regards