Welcome To the Hoffman Amplifiers Forum

September 08, 2025, 09:44:39 am
guest image
Welcome, Guest. Please login or register.
-User Name
-Password



Hoffman Amps Forum image Author Topic: 5f2a new build with Hoffman boards and parts no sound!  (Read 7693 times)

0 Members and 1 Guest are viewing this topic.

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
5f2a new build with Hoffman boards and parts no sound!
« on: April 22, 2016, 06:33:23 am »
Hi guys,
I'm brand new to building amps this is literally my first attempted.
I've completed the Hoffman 5f2a and it powers on my rectifier tube lights up but that's it no sound at all! The 6v6 and 12ax7 aren't glowing or getting warm to the touch ether.
I've traced the schematics a dozen times and I know I've done some rookie mistake I'm just lost! Any help would be greatly appreciated! I do have a multi meter but I'm not 100% sure how to test voltages. Thanks in advance and do not spare my feelings! I just want to learn and have this amp up and running.

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #1 on: April 22, 2016, 07:32:08 am »
Unlit tubes ain't gonna work, period, end of subject. There must be a wiring fault as to the green wires coming out of the power transformer. They, or their offspring, are just not reaching their intended destinations.


As far as a troubleshooting mindset, we first observe a problem. Then we try to imagine all the things that might cause our "no-go". (There could be multiple potential causes) Since we cannot see electrons flowing to or from or past something else, yet our meter CAN see such things, we try to devise scenarios and test them out as to whether they are true or not. We of course have to use the meter properly.


1: Amp does not play. What could cause that? (a hundred things) We turn it around or upside down and observe.
2: We see heaters unlit. We know that unlit tubes can not do their job. We then seek to isolate the specific thing that is making this so.


Either: the green wires or extensions of same are not getting to the tubes (BOTH of them, not just one, and presumably also not reaching the pilot lamp, this too being another clue) or....the transformer is defective and not putting out the 6.3-7 volts needed to light up the tubes and pilot. With experience, we massively discount the possibility of a brand new tranny being bad, because it's so rare. It is also possible that ALL THREE items, the 6V6, the 12AX7, and the pilot lamp are ALL bad, but the odds of that are infinitesimal. So we discard the possibility, pretty much. Astronomically unlikely.


But we COULD test that, in one of two ways. With meter on OHMS and power OFF, we could measure whether there is continuity from one end of the green-green winding to the other. We would want to pull the "6" tubes from their sockets because they will fool us. That winding that produces your heater volts should look almost like a short circuit to your meter. Another way, the two not being mutually exclusive, would be to power on the amp, set the meter to AC VOLTS and have our probes attached to the bare ends of the green-green. How do we do that? Doesn't that require three hands? Yes, it does, that's why we want an alligator clip or equivalent on the end(s) of our meter probes. Should read about 6.5 - 7 volts >>AC<<. Could be a failure to connect, eg; a wiring fault, or, the heater winding could be shorted out.


That's your problem. The green wires are not getting to pins 2 and 7 of the 6V6 tube nor the 4/5 + 9 on the 12AX7 nor the two terminals of the pilot lamp.


Could be bad solder joint.
Could be the layout omitted the connections (I have not looked at the Hoffman dwg) because this is a common thing to do, to assume that the heaters are wired up. You don't see them on the dwg, you forget to assume they have to be there.
Could be a broken mechanical connection somewhere. Guess what? NOBODY gonna wire them up but you!  :icon_biggrin:


Most likely, there is a wiring fault. You being a noob, more likely.


« Last Edit: April 22, 2016, 07:40:26 am by eleventeen »

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #2 on: April 22, 2016, 07:50:56 am »
Eleven teen,
Thanks for the reply!
I do have the heaters wired and that was my first thought that there is a bad connection. I have reflowed solder a couple of times! The pilot light does come on.
So I have the two solid green wires going to the pilot and then from there to the 6v6 and then 12ax7 so I'll go home after work and keep working that angle! I'll check voltages and see if I'm getting the proper reading. Thanks for your help!

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #3 on: April 22, 2016, 07:59:13 am »
In Fenders, it's typical to use the pilot lamp terminals as a junction point for connection downstream to the other tubes. If the pilot is lit we know the tranny is working and the other 6.3 volt items are not....it is the wires that connect from the pilot to the other tubes.


Probably you have those wires bunched inside the pilot lamp holder terminals and the "down the line" connection isn't getting to the tubes. You can measure AC volts on the heater pins of those tubes with the amp on and your caution mojo activated, OR, with POWER OFF test continuity with an OHMS meter setting or with an audio BEEP setting on the meter.


Amp needs to be ON to test volts. Amp needs to be OFF to test ohms/continuity.


VISUALLY, the wires are going from point A to point B. ELECTRICALLY, nope.
« Last Edit: April 22, 2016, 08:02:05 am by eleventeen »

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #4 on: April 22, 2016, 09:10:15 am »
By the way.....while you are fiddling with this.....[pull out the 5Y3 so that you are generating no high voltage DC while you test with power on.


You will STILL have high voltage >>AC<< on pins 4 & 6 of the 5Y3 socket, right? So be careful.

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #5 on: April 22, 2016, 09:23:15 am »
Maybe the filament wires are not connected to the correct socket pins? Look at the sockets from the bottom. The big socket has a key notch between pins 8 and 1. Pin 1 is clockwise from the key. Continue counting pins in a clockwise direction. The key for the little socket is a wide space between pins 9 and 1. Pin 1 is clockwise from the key. Continue counting pins in a clockwise direction. See pic...

If the wires are connected to the correct pins then you must have a bad wire or connection BETWEEN the lamp socket and the 6L6. A broken wire is more common when using solid core wire. The break is often right at the socket.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #6 on: April 22, 2016, 09:33:24 am »
Maybe the filament wires are not connected to the correct socket pins? Look at the sockets from the bottom. The big socket has a key notch between pins 8 and 1. Pin 1 is clockwise from the key. Continue counting pins in a clockwise direction. The key for the little socket is a wide space between pins 9 and 1. Pin 1 is clockwise from the key. Continue counting pins in a clockwise direction. See pic...

If the wires are connected to the correct pins then you must have a bad wire or connection BETWEEN the lamp socket and the 6L6. A broken wire is more common when using solid core wire. The break is often right at the socket.


Hey thanks I actually wrote each number on the side of the pin so I wouldn't make a mistake! I double and triple checked it as well. At this point I know it has to be the extension wires coming from the lamp to the 6v and 12ax7 that's going to be the thing I check next anyway.

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #7 on: April 22, 2016, 02:44:17 pm »
Okay. I'm home and started testing. I'm only getting 3.5v on the heaters.
What would be my next step? Does this mean the transformer isn't putting out properly? And is there a way to test that?

Offline pompeiisneaks

  • Level 3
  • ***
  • Posts: 1689
  • Tube is as Tube does
    • Daviszone
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #8 on: April 22, 2016, 02:51:24 pm »
I learned this one the hard way, that's fine.  The right way to read the entire heater voltage is to clip one lead on one side and the other on the second side.  you're only reading half of the voltage right now.  (or that's usually the case anyway).  Try reading it as I mentioned and see if you get around 6.3.

If you really ARE only getting 3.1 (or 3.5) then you've got one side of the rail not getting through.  Another good test is to put your meter on 'continuity' testing mode.  It should beep when you have a good connection, and do nothing if not (sometimes it beeps for a short time and then goes out, that means there's 'almost' continuity).  Turn it on continuity mode and touch one probe to the far end of the rail, and then touch each point on that side, then swap and do on the other (They should all read continuity, because they're on a circuit, but its just a way to try and see if something isn't getting down the rail)

~Phil
--
Phil Davis
tUber Nerd =|D

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #9 on: April 22, 2016, 03:16:35 pm »
Assuming your black or common test lead is on ground, eg; the chassis (very normal) this is because the center of the heater winding (typ green/yellow) is probably connected to that ground/chassis. (this is done for hum reasons not relevant to lighting up the tube or not) This turns the green-green heater winding in effect into two stacked 3.5 volt windings, arranged in series. With this center tap connection made; from ground to either green, 3.5 volts AC is exactly what you should read. The 6V6 and 12AX7 tube heaters are powered by the voltage existing between green and green. That is all they see, they do not care where green-yellow goes or if it goes anywhere. If you measure 3.5 volts AC from 6V6 pin 2 to ground and measure 3.5 volts AC from pin 7 to ground, you have the right voltages in the right place. If both of those tubes remain unlit, something very weird is going on. By the way, generally you can see the heater in the 12AX7 lit up (or not) thru the center hole of the tube socket for that tube, meaning, upside down, which is how one usually works on an amp chassis. Now see if with your meter on AC volts, you measure about 6.5 volts between pins 2 and 7 on the 6V6. You are doing this with the 5Y3 pulled out of its socket, right?
« Last Edit: April 22, 2016, 03:44:23 pm by eleventeen »

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #10 on: April 22, 2016, 05:00:24 pm »
Got it! It was the lamp! It would not pass current through one of the leads.
After putting a new one in all the tubes light and I'm getting proper voltage!
Now I'm still not getting sound so I'm assuming it's my speaker jack or input jack.
On the Hoffman diagram both leads from my output transformer are black but I have green and black for 8 ohms and then a yellow for 4 so I heat shank the end of it and left it alone. I used the black and green leads but my question is does it matter what lead of the jack they go to?

Offline shooter

  • Level 5
  • *******
  • Posts: 11016
  • Karma Loves haters
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #11 on: April 22, 2016, 06:25:08 pm »
Quote
does it matter what lead of the jack they go to?
It shouldn't unless you're concerned with phasing.
The input jack DOES matter, if that's backward the signal goes to ground.
Went Class C for efficiency

Offline Paul1453

  • Level 3
  • ***
  • Posts: 1085
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #12 on: April 22, 2016, 07:26:14 pm »
Got it! It was the lamp! It would not pass current through one of the leads.
After putting a new one in all the tubes light and I'm getting proper voltage!
Now I'm still not getting sound so I'm assuming it's my speaker jack or input jack.
On the Hoffman diagram both leads from my output transformer are black but I have green and black for 8 ohms and then a yellow for 4 so I heat shank the end of it and left it alone. I used the black and green leads but my question is does it matter what lead of the jack they go to?
Pictures are vital to getting good troubleshooting assistance.
The eagle eyed experts here can spot most problems from a good picture.

A pic from your cell phone or whatever will likely need to be adjusted to post here.
They will likely be too large of file size to post, so cropping and resizing will get the file down to a post-able size.
Doug has posted instructions to help you post pictures.
It's a lot easier for the picture to speak for you, than to try to write out what you have done.
A picture is worth 1000 words.  :icon_biggrin:

Welcome to the forum!  You will get your amp to work, I'm sure of it.   :icon_biggrin:

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #13 on: April 22, 2016, 08:00:10 pm »
I used the black and green leads but my question is does it matter what lead of the jack they go to?
Yes, it does matter since this amp uses NFB from the speaker. Try it one way, then reverse the leads. You should be able to hear which is the correct way to permanently connect the leads.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline shooter

  • Level 5
  • *******
  • Posts: 11016
  • Karma Loves haters
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #14 on: April 22, 2016, 08:30:57 pm »
Quote
this amp uses NFB from the speaker
:BangHead:
Went Class C for efficiency

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #15 on: April 22, 2016, 09:02:12 pm »
Okay Here are some pictures!
Anything you have is greatly appreciated.

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #16 on: April 22, 2016, 09:03:23 pm »
More pictures

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #17 on: April 22, 2016, 09:03:58 pm »
one more

Offline Willabe

  • Global Moderator
  • Level 5
  • ******
  • Posts: 10524
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #18 on: April 22, 2016, 09:50:42 pm »
I think your input jack hot/signal wire is shorted to ground? Can you move the red wire out of the way that's on top of the jack and take another picture so we can see better?

And what is going on in the purple circle?

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #19 on: April 22, 2016, 10:30:30 pm »
Heres a better pic!
The purple circle is the line off of the 12ax7 its grounded and going to the jack.

Offline Paul1453

  • Level 3
  • ***
  • Posts: 1085
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #20 on: April 22, 2016, 10:35:39 pm »
To me, it looks like everything on that jack is tied to Gnd.   :w2:

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #21 on: April 22, 2016, 10:40:42 pm »
So noting on the input jack should be grounded?

Offline Paul1453

  • Level 3
  • ***
  • Posts: 1085
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #22 on: April 22, 2016, 11:08:56 pm »
If your input signal is tied directly to ground, you will have a silent amp.

The input jack wiring is a little bit confusing at first, many people get it wrong when starting out.

See if you can figure out where your wiring deviates from the diagram.  :icon_biggrin:

Offline HotBluePlates

  • Global Moderator
  • Level 5
  • ******
  • Posts: 13127
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #23 on: April 23, 2016, 06:24:14 am »
Heres a better pic!
The purple circle is the line off of the 12ax7 its grounded and going to the jack.

It looks like one jack hasn't been wired up yet. Might be good to just remove that jack for now, so you don't plug into it by mistake and wonder why no sound.

The jack that is wired appears to have the following:
-  Sleeve (ground) and switched contact (middle lug) connected with bare wire; Good.
-  Bare wire ground connection from Sleeve to pots; Good.
-  1MΩ resistor from middle lug to Tip (hot); Good.
-  Black wire from Tip (hot) to Sleeve (ground); BAD. Signal is grounded right at the jack, nothing gets amplified (probably a misunderstanding of the schematic/layout symbol for a shield in a shielded cable, and its connection to ground).

You also appear to have the exact same issue on the Volume pot, with the middle & ground lugs connected by way of the red ground wire. This also shorts any/all signal to ground. It also appears to be a misunderstanding of the same symbol for a grounded shield in a shielded cable.

You have red wires which appear to run back to the board or tube from the volume & jack area. Those shouldn't be connected to the bare ground wire you have. They're also shorting your signal to ground.


At this point, don't assume you need to go adding shielded wire; I suspect it will create more problems than its solves at this moment. Just fix the wiring of the jack & volume control with the wire you have.
« Last Edit: April 23, 2016, 06:33:34 am by HotBluePlates »

Offline Willabe

  • Global Moderator
  • Level 5
  • ******
  • Posts: 10524
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #24 on: April 23, 2016, 08:09:45 am »
Is this a splice?

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #25 on: April 23, 2016, 08:36:17 am »
No it was stripped to be soldered to ground. "i.e." What I thought the diagram showed! After changing it and doing it right I have sound! But it sounds very overdriven and crackley

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #26 on: April 23, 2016, 09:36:16 am »
No it was stripped to be soldered to ground. "i.e." What I thought the diagram showed! After changing it and doing it right I have sound! But it sounds very overdriven and crackley
Now it's time to reverse the green and black wires on your speaker jack. If it sounds better leave them like that. If it sounds worse, put them back the way they were.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #27 on: April 23, 2016, 10:09:21 am »
Switched the leads in the output jack and everything seems to be working great!
My question now is that the amp has no cleans at all. Even with the volume nearly on it breaks up. Is there something I need to look at?

Offline HotBluePlates

  • Global Moderator
  • Level 5
  • ******
  • Posts: 13127
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #28 on: April 23, 2016, 10:29:19 am »
Is a wire connected to the middle lug of your tone pot? The picture was too dark there to tell.

A clear, big photo of the board & connections to the tubes would help at this point. Also, d.c. voltage measurements from every tube pin to ground (we can probably skip the 5Y3 tube for this).

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #29 on: April 23, 2016, 11:10:48 am »
Okay Here are some pictures and here are the dc readings on all the pins

6v6

1   15.3
2.  2.9
3.  1  .
4.  1   .
5.  00.0
6.  00.0
7.   2.9
8.   15.3

12ax7

1. 1   .
2. 00.0
3. 2.9
4. 2.9
5. 2.9
6. 1  .
7. 00.0
8. 2.8
9. 2.9

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #30 on: April 23, 2016, 11:11:32 am »
2

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #31 on: April 23, 2016, 11:13:22 am »
Here is better pics

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #32 on: April 23, 2016, 11:14:02 am »
another

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #33 on: April 23, 2016, 11:50:55 am »

You're not setting or changing your meter to the correct range or AC vs DC properly. Or your meter can't or is not designed to read >200 volts. The only place(s) you are measuring AC is on heater pins: 2 & 7 on 6V6 and 4/5 & 9 on the 12AX7. All other measurements are DC. But since the tubes are now lit up, forget AC.

Okay Here are some pictures and here are the dc readings on all the pins
6v61   15.3  <--plausible   
2.  2.9    <--close, this is where you ought to be seeing ~~3 volts (assuming gnded CT on green-green heater wires) but the tubes are lit up now, so let's forget this.  This is >>AC<<. A DC measurment should show 0 or very very low volts.
 

3.  1  .   <---Is this your meter saying "overrange"? Should be 300 or some-odd BIG volts. Is the 5Y3 in? No DC volts without him in the socket and one of your hands IN YOUR POCKET. 5Y3 in socket and one hand in pocketŠ  :icon_biggrin:
4.  1   .  <---same as above, screen grid, should be BIG DC volts.   
 5.  00.0  <--right!   
6.  00.0  <--right   
7.   2.9   <---heater, should read ~~3 VAC   
8.   15.3  <--plausible   
12ax7  1. 1   . <---a plate, should be in the +200 VDC range (could be 170-220) 
2. 00.0  <---right   
3. 2.9   <---little high, but OK. 
4. 2.9   <---heater, this is AC   
5. 2.9   <--common w/pin 4 = heater 
6. 1  .  <--the other plate, should be ~~200   
7. 00.0  <---right   
8. 2.8   <--little high, but OK   
9. 2.9   < heater, this is AC   

Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #34 on: April 23, 2016, 12:13:35 pm »
Ok new readings!
Sorry I'm so new to this.

6v6

1.  7.34
2.  2.9 dc
3.  385
4.  125.6
5.  4.9
6.  4.9
7.  2.9 dc
8.  7.35


12ax7

1.  198
2.  No reading just  noise
3.  1.66
4.  2.9 dc
5.  2.9 dc
6.  194.3
7.  No reading just noise
8.  1.63
9.  2.9 dc

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #35 on: April 23, 2016, 12:57:38 pm »
You have a 470K resistor where a 470Ω resistor should be. That accounts for the very low voltage on the 6V6 pin 4. It probably accounts for the distortion. If you don't have a 470 ohm resistor to replace the 470K resistor you can just replace the 470K with a jumper wire. The original 5F2A did not use a resistor in that position. Your amp will work just fine but using a 470Ω resistor is preferred. See pic. I circled the resistor that needs to be replaced with a jumper wire or a 470Ω 3 watt resistor.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline eleventeen

  • Level 4
  • *****
  • Posts: 2229
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #36 on: April 23, 2016, 01:04:09 pm »
Good catch, Sluckey!!


I and my old eyes have trouble reading the color bands on those blue resistors, so I always measure them before soldering them in. Especially on the little 1/2 watt ones, I don't even try to read them.


On the other hand, any old resistor these days seems to be within 1-2% which in the old days was a "wow! precision resistor!". Even ordinary resistors are very often within 1% of spec.



Offline makingnoise88

  • Level 2
  • **
  • Posts: 104
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #37 on: April 23, 2016, 01:16:42 pm »
Oh my gosh that was it! This thing rips! Thank you all for your help!

Offline Paul1453

  • Level 3
  • ***
  • Posts: 1085
  • I love Tube amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #38 on: April 23, 2016, 01:34:23 pm »
Congratulations!

I told you that you would get that thing going!

Offline sluckey

  • Level 5
  • *******
  • Posts: 5075
    • Sluckey Amps
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #39 on: April 23, 2016, 02:34:54 pm »
Now it's time to reverse the green and black wires on your speaker jack. If it sounds better leave them like that. If it sounds worse, put them back the way they were.
Now that the amp is ripping I would try this suggestion once more. There should be a big difference between right and wrong now.
A schematic, layout, and hi-rez pics are very useful for troubleshooting your amp. Don't wait to be asked. JUST DO IT!

Offline sean_thornton

  • Level 1
  • *
  • Posts: 51
Hoffman Amps Forum image
Re: 5f2a new build with Hoffman boards and parts no sound!
« Reply #40 on: May 01, 2016, 11:33:19 am »
This is why i love this forum. New guy comes in with a problem and everybody that can help pitches in until it gets sorted out. No mockery, no dramas, just good solid technical help. I wish all internet forums were this good.

 


Choose a link from the
Hoffman Amplifiers parts catalog
Mobile Device
Catalog Link
Yard Sale
Discontinued
Misc. Hardware
What's New Board Building
 Parts
Amp trim
Handles
Lamps
Diodes
Hoffman Turret
 Boards
Channel
Switching
Resistors Fender Eyelet
 Boards
Screws/Nuts
Washers
Jacks/Plugs
Connectors
Misc Eyelet
Boards
Tools
Capacitors Custom Boards
Tubes
Valves
Pots
Knobs
Fuses/Cords Chassis
Tube
Sockets
Switches Wire
Cable


Handy Links
Tube Amp Library
Tube Amp
Schematics library
Design a custom Eyelet or
Turret Board
DIY Layout Creator
File analyzer program
DIY Layout Creator
File library
Transformer Wiring
Diagrams
Hoffmanamps
Facebook page
Hoffman Amplifiers
Discount Program


password