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Old 13th Sep 2019, 6:48 pm   #161
Guitarist28
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Default Re: Shaftesbury 519 amplifier

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?
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Old 13th Sep 2019, 6:51 pm   #162
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Default Re: Shaftesbury 519 amplifier

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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.

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Old 13th Sep 2019, 6:56 pm   #163
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Default Re: Shaftesbury 519 amplifier

Thank you Lawrence and apologies as mixed you with another forum member.
Best regards
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Old 13th Sep 2019, 8:01 pm   #164
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Default Re: Shaftesbury 519 amplifier

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.
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Old 13th Sep 2019, 8:11 pm   #165
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Default Re: Shaftesbury 519 amplifier

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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
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Old 14th Sep 2019, 4:17 pm   #166
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Default Re: Shaftesbury 519 amplifier

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.
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Old 14th Sep 2019, 9:56 pm   #167
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Default Re: Shaftesbury 519 amplifier

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!
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Old 14th Sep 2019, 10:07 pm   #168
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Default Re: Shaftesbury 519 amplifier

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

https://www.youtube.com/watch?v=6UzFW0dPF5E
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Old 14th Sep 2019, 10:31 pm   #169
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Default Re: Shaftesbury 519 amplifier

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?
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Old Yesterday, 10:03 am   #170
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Default Re: Shaftesbury 519 amplifier

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Originally Posted by Guitarist28 View Post
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.
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Old Yesterday, 10:17 am   #171
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Default Re: Shaftesbury 519 amplifier

Quote:
Originally Posted by Edward Huggins View Post
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.
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Old Yesterday, 10:57 am   #172
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Default Re: Shaftesbury 519 amplifier

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.
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Old Yesterday, 1:34 pm   #173
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Default Re: Shaftesbury 519 amplifier

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Originally Posted by Guitarist28 View Post
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.
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Old Yesterday, 2:04 pm   #174
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Default Re: Shaftesbury 519 amplifier

2nd revision.

Lawrence.
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