13th Sep 2019, 6:48 pm | #161 |
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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? |
13th Sep 2019, 6:51 pm | #162 |
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Re: Shaftesbury 519 amplifier
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. Last edited by ms660; 13th Sep 2019 at 6:57 pm. |
13th Sep 2019, 6:56 pm | #163 |
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Re: Shaftesbury 519 amplifier
Thank you Lawrence and apologies as mixed you with another forum member.
Best regards |
13th Sep 2019, 8:01 pm | #164 |
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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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13th Sep 2019, 8:11 pm | #165 | |
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Re: Shaftesbury 519 amplifier
Quote:
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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14th Sep 2019, 4:17 pm | #166 |
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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. |
14th Sep 2019, 9:56 pm | #167 |
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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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14th Sep 2019, 10:07 pm | #168 |
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Re: Shaftesbury 519 amplifier
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14th Sep 2019, 10:31 pm | #169 |
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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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15th Sep 2019, 10:03 am | #170 | |
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Re: Shaftesbury 519 amplifier
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Nice SG. Lawrence. |
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15th Sep 2019, 10:17 am | #171 | |
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Re: Shaftesbury 519 amplifier
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Lawrence. |
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15th Sep 2019, 10:57 am | #172 |
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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. |
15th Sep 2019, 1:34 pm | #173 | |
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Re: Shaftesbury 519 amplifier
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2nd revision version later on. Lawrence. |
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15th Sep 2019, 2:04 pm | #174 |
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Re: Shaftesbury 519 amplifier
2nd revision.
Lawrence. |
16th Sep 2019, 3:55 pm | #175 |
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Re: Shaftesbury 519 amplifier
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 |