As a voltage divider.
Lug 2 would be the output.

Cool project. 

May I suggest that you will need some kind of "tone shaping" in that amp.
Guitars just don't sound good played thru a "HiFi flat response" type of amp.

If you have a home stereo, try playing your guitar thru it,
possibly getting some adapter and using the phono input if it has one.

Of course the speaker will have a huge impact on the sound.
If you use a "real" guitar speaker that will help.

I have been playing around with this circuit...

http://www.muzique.com/lab/notch.htm

You can add this circuit inside and not even use a "tone" control.
It will give you a "notched mid" response which helps prevent the tone from being muddy.
A very useful circuit, I have added it to a couple of amps and played around with the values.
Made some crappy sounding amps sound great!

Cheers!

Quote from: ilyaa on August 07, 2017, 11:51:08 AM
no one have any thoughts on where to get green heatsink tape?

all the stuff I'm finding is double-sided and made for ICs - comes in squares

the tape on the Yamaha output transistor heatsink is greenish and one-sided and clearly comes in a roll -

Maybe some Kapton tape? probably not available local to you...

How about some Mica insulators?

C71 looks bad, did you replace it?

If C71 is shorted it could put DC on the speaker.

Disconnect the speaker and connect a multimeter set to DC volts to the amp output. (where the speaker would normally connect)

Switch on the amp. Is there a DC voltage reading on the speaker output? How much?

I see there is a Carlsbro company in the UK. Their logo says "since 1959".

Might be worth it to contact them and ask if they have any "legacy" product info, ie: a schematic for your amp.

http://www.carlsbro.com/

A schematic would be handy but a quick Google search doesn't turn up much...

These guys have some but I don't see the Hornet...

http://www.amprepairparts.com/schematics.htm

I don't suppose much chance there is a schem pasted inside the amp somewhere?

Just my 0.02

My first thought is that some electrolytic caps have gone bad/dried up, esp if there are any small value electros in the audio path.

I've been tinkering with older 70's / 80's SS amps lately, and found several that instantly sound "better" when I replace those small value electro cap that are in the signal path.

No doubt some better minds will chime in with ideas/experience. 

Edit; none of those caps I replaced tested bad or "looked" bad, ie, no leaking/swelling etc, but nevertheless the amp(s) sounded better once they were replaced.

... and, I often installed non-electro caps in place of them, usually with those small box film types of 1uF or less.

Thanks!
It sounds pretty good with the Weber speaker (originally intended for the Vibro Champ).
Not very loud tho...

That's ok, it could keep up with a moderately loud rehearsal.

New output TX came in.

Amp is working again, Yay. 

Cool. 

Thanks Enzo.

Hopefully when the new O/T gets here, it will have something to ID the leads.

Edit; Oh... yes it does...  I ordered this one...

https://www.amplifiedparts.com/products/transformer-hammond-output-replacement-fender-5w-7k

Sooooo, as per the schematic attached above, the original O/T secondary went straight to the speaker.
No connection to the chassis.

Since I am installing a speaker jack,
I have the option of installing an insulated jack that obviously, would also not make any connection to the chassis.

If I were to install a non-insulated jack, would it then make some difference as to which side of the secondary should be connected to the ground side of the jack?
IOW, is there a phasing issue that I need to be concerned about?

TIA

Thanks JM,... but

Naaaah  the transformer is gakked!

I peeled back some of the lacquered paper and the drill bit went in right between the thick sec wind and the tiny primary.
With the paper peeled back I can see several broken primary winds right in the middle.

Only way to save this one would be a rewind. Probably not worth it.

I'll keep it with the amp for posterity. 

Just thought I'd throw up a schematic for this...

Quote from: joecool85 on June 19, 2017, 06:05:50 AM

Bummer. However I feel for you. I did a similar thing where I was putting a heat shield back onto my wife's car. I had to drill a hole for the rivet and it was to go into the spare tire housing...I didn't remove the tire first. Made for a funny moment at the tire shop when I told them I drilled the tire LOL.

Sent from my XT1055 using Tapatalk

Thanks Joe, that's a funny story.   

Ya, I'm sure anyone that works with their hands has messed up somewhere, sometime, and done something boneheaded.
I know I have, and not just when working on music gear.

I've been in the transmission repair industry for nigh on 40 years now and have witnessed, and done, some really stupid things.

One doozy I'll never forget....

Taxi cab came in the shop cuz the tranny is not working... Ford Crown Vic rear wheel drive.
Ok, so pull the tranny out see whats broken...

The guy pulling the tranny removed every single bolt holding the tranny in the car and it refused to come out...
Like it was "stuck" up in the car... WTH.

Turns out the driver had it at a place to install "Taxi cab gear" you know, the meter and radio and such...

Well they mounted it on the transmission hump and.... surely you can guess now...

Yup, they use reeeely long screws and drilled and screwed right down into the transmission to install the meter and radio. DOH!

Glad it wasn't me that did that!

(you didn't think I was gonna tell of any of my boneheaded screw ups, didja 
this one with drilling the Tx was enough.

Thanks Enzo,

Yes, I should do more checking.... however...

I'm embarrassed to admit.... "I" may be the cause of the failed transformer.

You see, I drilled a hole for the secondary wires to go inside the chassis so I could install the speaker jack.

Foolishly I did this with the transformer still bolted in place... do you see where this is going....

That's right, the tiny pilot drill I used, punched through the chassis and nicked the winding's.  :grr

I then of course, removed the Tx and made the hole big enough to install a grommet for the wires.

Then inspected the Tx carefully with a magnifying glass and did not see any real damage, but the drill bit did go a small ways into the winding.

Fairly sure I screwed it up.