Solid State Guitar Amp Forum | DIY Guitar Amplifiers

Solid State Amplifiers => The Newcomer's Forum => Topic started by: GlenF on May 04, 2019, 09:47:00 PM

Title: Heathkit TA16
Post by: GlenF on May 04, 2019, 09:47:00 PM
Hello everyone.  I have an old Heathkit TA16 giutar amp my dad built for me when I was a kid.  I wanted to bring it back out and start playing again, but when I plugged it in, nothing.  I am no electrical wizard, but I can learn with help.  I have worked on it before and had it working, but there is no sound now.  Where do I start?  Any help would be great!  Thanks in advance.
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 04, 2019, 11:52:26 PM
Can you help out a bit and define 'nothing'?

No lamp light, no sound?

It would be a nice gesture to include the schematic when asking for assistance.
 That said, the schematic itself is only a road map.
What is typically not provided is the board layout.

So you will have to muddle through and possibly trace out and draw sections that are in question.
The first place to start is the power supply.
Are all supplies up & running?

Title: Re: Heathkit TA16
Post by: GlenF on May 05, 2019, 10:33:45 AM
Thanks for getting back to me!  I have a power light, bur no sound.
Here is the site I got the schematic from.

https://elektrotanya.com/heathkit_ta-16_guitar_amplifier_sch.pdf/download.html

Hope this helps.
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 05, 2019, 03:12:17 PM
Ok. The lamp is lit.
That means you have voltage on the secondary of the power transformer.
Your next step is to verify the dc supplies.
there are 5 of them.
I would start at the +38Vdc rail.

A word of caution.
Being that this is a direct coupled power amplifier, I would advise removing the speaker load until you get things sorted out.
Title: Re: Heathkit TA16
Post by: GlenF on May 05, 2019, 04:10:06 PM
I'm not sure where the +38Vdc rail is, and how do I remove the speaker load?  I'm not an electrician, but I want to learn more about these things.
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 07, 2019, 11:34:33 AM
"So you will have to muddle through and possibly trace out and draw sections that are in question."
Title: Re: Heathkit TA16
Post by: phatt on May 08, 2019, 07:34:10 AM
Hi Glen,
         Yes hard to know where to start but *JazzBass* means disconnect the speaker,,  the Amp drives a load which is the speaker. Load is tek talk for the speaker. ;)
Assuming you have a meter,, set it to the highest DC voltage.

With speaker disconnected probe the output speaker terminals/wires and it should be very close to Zero VDC less than 0.5VDC.
Now with Ground probe on chassis the first DC supply is found at the output of the Bridge rectifier. (Marked G)  The rectifier is those 4 diodes marked D102 to D105.

(J) is common or ground and often also connected to Chassis but not always.

The voltages are on the schematic,, if not sure where they are on the circuit then often the Electrolytic caps will give you a clue as to where to find those voltage nodes.
they will not read Exactly the same but as long as they read close it's all good.

Some old amp layouts are quite dangerous so be aware of the mains input wires it can KILL you.  8|
 I Cover any bare terminals that hold mains voltages when I have to work on that stuff.
Phil.
Title: Re: Heathkit TA16
Post by: GlenF on May 08, 2019, 08:33:59 PM
I have the board out of the amp right now.  To do the tests, do I need to have it plugged into the wall so that there is power to the board or can I do the tests unplugged?
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 09, 2019, 11:03:33 AM
Yes, the unit must be plugged into the wall outlet.
Power switch On.

Keep in mind you are measuring dc voltages.
So your meter must be set to read Volts dc.
Title: Re: Heathkit TA16
Post by: GlenF on May 09, 2019, 10:23:02 PM
Before I start to take readings, there is alot of brownish stains on the outside of the solder.  Is this exess flux, and could this be part of the problem?
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 10, 2019, 01:33:51 AM
Can you upload a pic?
Title: Re: Heathkit TA16
Post by: GlenF on May 10, 2019, 05:57:24 PM
 I have tried three times to upload a pic.  It keeps telling me the file size is too large.  Not sure what to do now.
Title: Re: Heathkit TA16
Post by: Den. on May 10, 2019, 06:53:34 PM
I have tried three times to upload a pic. Not sure what to do now.

Look here https://tinyurl.com/yyshve6g (https://tinyurl.com/yyshve6g) for a solution.
Title: Re: Heathkit TA16
Post by: GlenF on May 10, 2019, 07:04:32 PM
Thanks for the help Den!
Title: Re: Heathkit TA16
Post by: phatt on May 10, 2019, 10:01:09 PM
That is *Normal flux residue* and has no effect on circuit. :tu:

Re file size,
When you load attachments it tells you the file size limit;
*maximum individual size 5120KB*

If it helps,,
Download this; https://www.irfanview.com/
I've used this for years and could not work without it <3) <3)

Does just about anything you throw at it,,, and it's FREE! :dbtu: :dbtu:

Load your pic and from the drop down menu called *Image* click *Resize/Resample* (or hit Control R)
Now click on *Half size*,, hit OK.
 Then  *Save AS* select *File Type* as a *JPEG*

That will reduce a 7Meg file down to  maybe 500kb.
Don't forget to rename the file if you want to keep the original. 8|
HTH, Phil.
Title: Re: Heathkit TA16
Post by: Jazz P Bass on May 11, 2019, 12:15:28 AM
From the pic I can see a few solder joints that appear 'iffy'.

Not too sure what soldering iron or skill set the OP has.
Title: Re: Heathkit TA16
Post by: GlenF on May 11, 2019, 08:20:09 AM
I'm certainly no pro, like you guys.  If you could give me some pointers, that would be great!  My dad did the majority of the work back in the early 70's, and I changed a few wires 5 years ago.  If you could point out which joints look iffy, I could redo them. 
Title: Re: Heathkit TA16
Post by: phatt on May 11, 2019, 09:48:32 AM
Nope ya goin' the wrong way, could lead to more mistakes xP
 Establish those voltages FIRST. 8|
The pic quality is good but we need the whole board
Some good clear pics of both sides of the board will help a lot ;)
Phil.
Title: Re: Heathkit TA16
Post by: GlenF on May 11, 2019, 10:10:29 AM
Thanks Phil.
Title: Re: Heathkit TA16
Post by: GlenF on May 11, 2019, 10:12:34 AM
And the other side.
Title: Re: Heathkit TA16
Post by: GlenF on May 12, 2019, 09:06:53 AM
And the meter I have.
Title: Re: Heathkit TA16
Post by: GlenF on May 12, 2019, 09:51:39 AM
I think I am the right path.  In the pic, there are 4 little black diodes (I think that's what they are).  When I test the 2 on the left, I get readings from the top lead, but not the bottom.  On the right 2, I get readings from both ends.  Is this normal?
Title: Re: Heathkit TA16
Post by: galaxiex on May 12, 2019, 12:12:57 PM
You might benefit from having the complete construction manual for that amp.

It is available here>>>  http://www.vintagemanuals.com/manual/Heathkit/TA-16 (http://www.vintagemanuals.com/manual/Heathkit/TA-16)

for a reasonable price.

Heathkit manuals are very well done (step by step) and have a trouble shooting section to help diagnose problems.
You will learn a lot just reading the manual.

If you decide to get the manual, be sure to go to their home page and read the ordering info and about their manuals.

http://www.vintagemanuals.com/mission.html (http://www.vintagemanuals.com/mission.html)

 :)
Title: Re: Heathkit TA16
Post by: GlenF on May 12, 2019, 10:33:44 PM
I'll look into that.  Thanks for the info!