Vox Essex bass amp? Anyone got one to take some pictures??

[R.G.]

I'm working on a Repair Supplement to the Vox Owner's Safety Net manual for the Essex line of Thomas Vox amps. I have the original repair guides from Thomas, but the preamp was constructed on tag board and I don't have pictures of that. I've scoured central Texas, and can't find one either. Could I prevail on an Essex owner to take a few pictures inside the amp?

[Leo_Gnardo]

RG! Your lucky day, maybe. Took a snap for you inside an Essex abandoned here years ago. Gnarly hand built on tag strips all right. Let me know if you need any detail shots. This came out unexpectedly well, hope it helps.

[Tassieviking]

I would love to see the schematic for that one, just don't ask me to trace it.
I wonder how much planning went into that layout to make it that neat and tidy.

[loudthud]

Wasn't there a Heathkit version of that amp ?

Vox/Thomas Service Manual: (Hope this link works)
https://music-electronics-forum.com/attachment.php?attachmentid=44358

[R.G.]

Wow Leo! My lucky day indeed! Thank you.
Would you prefer to be credited by your group handle, actual name, or not at all? (I've run into some people who want to remain anonymous)

@TassieViking: As L.T. mentions, it's in the Thomas Organ service literature. I can post it here if the link doesn't work.
@ L.T.: the link doesn't work for me. None of the links to attachments or schematics work for me, for some reason.

Edit: that picture is of the bottom of the control panel for an Essex V1042 or V1043. The V104 had only a one-transistor "preamp". The V1041 adds a two-transistor limiter. The V1042 and V1043 have the two-transistor Tone-X switching circuit shown on the bottom tag strip. It got gnarly by accretion, like a coral reef - they just kept adding on more tagstrip stuff to make new models. If it had a tuner module on the cabinet back panel, it's a V1043, the last one in the series.

[Mick Bailey]

That's an impressively clean amp. The unsupported inductor hanging on by its leads looks interesting.

[Leo_Gnardo]

Wow Leo! My lucky day indeed! Thank you.
Would you prefer to be credited by your group handle, actual name, or not at all?

MY lucky day, the day I can do something for the Notorious R.G. Wow, I get a photo credit? Leo Gnardo will do just fine, much obliged!

How about the power amp inside? I'm muddling thru a project at the moment (rebuilding a Marantz 15 hi fi amp, slow slow going) but if you need the power amp photo let me know, I'll get to it later on.

[g1]

Wasn't there a Heathkit version of that amp ?

Vox/Thomas Service Manual: (Hope this link works)
https://music-electronics-forum.com/attachment.php?attachmentid=44358

That one didn't work, but this links to what should be the same Essex svce. manual: https://music-electronics-forum.com/...chmentid=44358

[R.G.]

MY lucky day, the day I can do something for the Notorious R.G. Wow, I get a photo credit? Leo Gnardo will do just fine, much obliged!
/QUOTE]
Absolutely you get photo credit. BOTH people who eventually buy a copy will see it.
Oh, wait. All three people. PM me your address and I'll send you a copy when it gets put up for publishing.

/QUOTE]
How about the power amp inside? I'm muddling thru a project at the moment (rebuilding a Marantz 15 hi fi amp, slow slow going) but if you need the power amp photo let me know, I'll get to it later on.

If you feel inclined, sure, I'd love it. I have a photo of the power supply/amp chassis inside the cabinet, but if you feel like opening it up and snapping some shots inside it, that would be a very thick layer of icing on the cake. And it's also OK if you don't feel inclined now or in the future.

Near as I can tell, the power supply and power amplifier chassis was re-used from a previous Thomas Organ organ. If the factory service lit can be believed, only about half the PCB is populated, that being just the power amp circuits. As expensive as PCBs were in the early 1960s, I can't feature Thomas making a new PCB for the Essex, and making it 2X too big, as well as empty.

[So80s]

Hello R.G, I have acquired what may be a 1965 Essex bass amp, however I cannot find the correct schematic. If you or anyone can provide a proper schematic and or any repair documentation that would be great? I have the 4A schematic but it is not correct, for example it has too many transistors. I have attached some photos, including a photo of the PCB in hopes someone can direct me to the correct schematic.

My father is an electrical engineer and he is trying to locate the cause of a loud hum and based on reading this forum I understand there can be various causes. He already checked all the capacitors and that doesn't appear to be the issue. Without the proper schematic we are kind of stuck. Thanks for any assistance. Have a good day.

[So80s]

Please ignore the yellow clip lead in the photo of the PCB. That's just a connection we made during testing.

[The Dude]

The only schematic I have is the same as the one g1 provided in post #8. Is that not the one for your amp? It's been a while since I've seen one of these on the bench, so excuse if I'm remembering incorrectly. Is this the amp with the power supply/amp in one chassis and the preamp in another? If so, I recall having to relocate the power switch to the power supply chassis. If you look, AC power runs right along side the preamp send wires to the power amp in the same connector. 120V of AC right next to a low level signal wire is not a good idea. I disconnected the power wires going up to the preamp which contains the power switch, and located a power switch closer to the power input in the amp chassis. It was the only way to get the amp quieter. This all assumes I'm thinking of the correct amp. Of course, I haven't heard the amp you are working on, so there could be other bigger problems.

[loudthud]

So80s, The PCB pic you posted in reply 10 has the same number, 25-5160-2 as the one shown in the link G1 posted in reply #8. There may be slight differences between the PCB assembly in your amp compared to the service manual, but they should be minor. Try to decipher the exact model of your amp from the descriptions in R.G.'s reply #5.

[So80s]

Thank you very much for your responses. Sorry for the delay in responding but I broke my phone. I will try and determine my model from the number on the PCB. Thank you for that suggestion. My Dad is going to verify if the schematic posted it in #8 is correct or not.

Does anyone know if the original repair guides for the Essex line from Thomas Organ are available anywhere? I'm trying to find repair information.

RG stated he is working on a supplement but I'm not sure where to find any produced documentation. If anyone has any links it would be greatly appreciated.

Thank you. Have a good day.