Hi there,
This is my first post here so firstly hello.
I've just scored a used Pignose Hog 20 amp. I got it for $20 but I not sure its not working. It all looks good. I'd say the batteries are toast from lack of use. But I'm not sure of what kind of power adaptor to get it's 12VDC but I don't know the mA rating. And also whether I can run it without the batteries in it. I would like to get it going before I spend $50-60 on 2 new batteries for it.
So I guess my question is, is there anyone on here that has experience with this little amp, a copy of the manual and perhaps a schematic.
cheers
mike
So after a few days trolling the net I happened across Jim McBride's www.bottle-o-blues.com
Jim makes the bottle-o-blues harmonica microphone. He all so sells the Pignose Hog 20. Jim helpful told me that the power supply that he has for the pignose is a 12v 1500mA one.
So tommorow I'll go and get one and see if I can get my Pignose going.
Also having had a closer look at it I think it should run without the batteries in it, so thats cool. Its actually a neat little amp the chassis once unscrewed from the cabinet comes out totally leaving the cabinet with only the speaker in it. So it'd be an easy amp to completly replace the amp with something else and just hook up the speaker.
I'd still be greatful for any more info about this amp. A manual or Schematic.
Cheers
mike
Wow I'm supprised no one has any info on this amp?
Anyhow I got a 12VDC 1500mA power adapter yesterday and its up and running again. :) Although theres a slight hum or buzz going on like a bad earth. :(
It does run without the batteries in there so thats cool. If you haven't seen one of these the way its design is quite cool. They've used connectors for a few things onto the circuit board.
Both the input jacks and the headphone jack have these and can be unconnected from the board.
I've removed both the front and back inputs as they had plastic threads and had both stripped. I'm not sure how these were wired but they both look like stereo inputs (well they have 9 lugs) the back one is wired to the front one and the front one has 2 wires going to the circuit board. Not sure if there is some switching in there or not.
heres how its wired
(http://farm3.static.flickr.com/2571/3687903491_6dc91e2096_o.jpg)
Rear input Front Input
Anyone know whats going on here?
I've just replaced the front one with a new mono input and it seems to be working okay.
Its actually quite loud. More than enough for our 1 bedroom flat. I could see how cool it would be with the batteries in it.
Its built in distortion leaves a bit to be desired, not to my taste anyhow. But with a overdrive or distortion pedal in front of it, it sounds okay.
Hi Highplains. Well, there´s not info on many popular amps, even less on this excellent yet less sold one. Besides, Pignose usually tries to not give too much details. <Most what´s known about them, comes from curious end users like us. Would you please post some photos of its guts? It would be very interesting. Thanks.
I had a Hog 20. Gave it to my brother and wish I had it back.
It uses 2 six volt 4AH SLA batteries, wired in series. Don't overcharge them.
A very sweet sounding amp. My Korg Pandora PX4 sounded better with the Hog 20 than any other amp.
Carl
I know this is an old thread, but I came here by a search-engine looking for the schematics.
Just want to post, if someone else is searching...
Best
Hi diyfalk, thanks a lot for posting.
Many wanted to know it. :dbtu:
I am trying to repair mine. :)
There where some faults i could fix, but not yet all.
For example, the Switch of the Squeal Pot was broken, thats the reason i build in a new one.
What i didn't know before ordering was, that it should have been an opener switch.
I bought a Closer... :-(
For the moment that is ok, cause i do not need the distortion.
If someone here has an idea where to get one here in europe let me know.
I can buy one from Pignose directly, but the shippingcosts will be much higher than the pot.
Then another fault was the Input-Connector on the backside.
I build in a normal Connector, cause i do not need the switching.
Then the Tone-Pot had a loos connection. I could fix that by cleaning it.
So now the last thing what i think is broken is the TDA7240.
With headphones the sound is quiet fine, but when i hear over the speaker, it is strange.
If the sound is loud it is free from distortion. If than the guitartone gets quieter the distortion starts.
So normally i would expect that it is the way round but it isn't.
The loudspeaker is ok, i checked it.
So after changing the TDA (maybe this week), i will try new caps.
Hopefully some day it will sound fine again. ;)
I never heard him playing right...
Quote from: diyfalk on March 12, 2013, 11:58:22 PMthe Switch of the Squeal Pot was broken, thats the reason i build in a new one.
What i didn't know before ordering was, that it should have been an opener switch.
I bought a Closer...
No, you need the "regular" switched pot: on "0" the switch is open, and the clipping diodes are out of the circuit; on "1" and higher the diodes are connected and it starts clipping, raising the Squeal pot it clips more.
That said, that distortion circuit is horrible :( , don't waste time on it.
QuoteFor the moment that is ok, cause i do not need the distortion.
If someone here has an idea where to get one here in europe let me know.
I can buy one from Pignose directly, but the shippingcosts will be much higher than the pot.
You already have the correct pot/switch.
QuoteThen another fault was the Input-Connector on the backside.
I build in a normal Connector, cause i do not need the switching.
Post a picture, it is not on the PCB.
QuoteThen the Tone-Pot had a loos connection. I could fix that by cleaning it
Maybe. Although you might have to replace it.
QuoteSo now the last thing what i think is broken is the TDA7240.
With headphones the sound is quiet fine, but when i hear over the speaker, it is strange.
If the sound is loud it is free from distortion. If than the guitartone gets quieter the distortion starts.
So normally i would expect that it is the way round but it isn't.
That does not sound like a broken TDA7240 at all but like a bad speaker.
Connect another speaker to check it.
QuoteThe loudspeaker is ok, i checked it.
Not so sure, connect the amp to another speaker.
QuoteSo after changing the TDA (maybe this week), i will try new caps.
What you are doing is called "shotgunning", replacing parts at random trying to find the problem.
Bad news: it does not work that way :(
You will never ever find a problem that is not caused by "bad parts", such as a bad connection, poor soldering, cracked track, etc.
In fact, I very much suspect the phone connector (labelled "PHNOE" on the schematic) which has an internal leaf switch which may be dirty/worn/weak/rusty/all of the above.
Squirt a little contact cleaner or at least some WD40 into it and plug in/out the proper plug a few times to clean it.
Or momentarily solder a wire across the switch contacts.
Please measure and post voltage on 7240 pins 3/5/6/7 .
Thanks.
Quote from: diyfalkWith headphones the sound is quiet fine, but when i hear over the speaker, it is strange.
If the sound is loud it is free from distortion. If than the guitartone gets quieter the distortion starts.
I agree with
JM, your description is classic of speaker (or speaker connection) trouble. You don't want to replace the chip amp only to find that you still have the same fault.
JM calls it "shotgunning", I call it the "blunderbuss method", but whatever you call it replacing parts based on
guessing doesn't work. When you go to a doctor they don't guess on sight but take measurements, poke you to see where it hurts, and repairing amps is the same; we take measurements, try some tests, and see where those lead us.
Then we perform surgery.
A different test here is to connect the amp to a different speaker cab and see if it still shows the same "dirty at low level" fault; but when you say it sounds okay on headphones that pretty much clears the chip amp and points the finger at the speaker (which the headphones substitute for).
I don't know where you are in Europe, but I regularly get
Elektor magazine which is a European publication which contains adverts from many parts suppliers, so I suggest you try Googling "electronics parts suppliers <your country>" and you should find quite a few retailers.
Farnell <www.farnell.com (http://www.farnell.com)> also trading as
Element14,
Maplin (UK), and
Jaycar come to mind.
Many, many thanks for the support!
Ich will check the phone-connector with soldering a wire over the switch.
And let you know.
Thank you so far.
Good idea with Elektor and farnell.
I live in .de
best
Here are my measurements on the TDA 7240 in DC
Ground to
Pin 3=5,62 V (Input)
Pin 5=5,67 V (Output)
Pin 6=12,08 V (Supply Voltage)
Pin 7=5,74 V (Output)
next i will test with another speaker and let you know.
Too bad that i can not upload a video (.mov) with the mistake...
hello friends,
i checked now with my ac-30 cabinet and it is still the same problem.
When the sound is getting quieter the more distortion came.
hm... :loco
But still clean on headphones?
Was the AC-30 speaker test with the headphone switch contact bridged by wire?
Check that the voltage on pin 2 (SVR and Standby) is well above 1 volt.
To test the Pignose speaker, disconnect it from the Pignose amp and drive it (gently) from the AC-30 output - fault or no fault?
Set the Pignose volume and tone controls to half way (5/10) and inject a signal from an MP3 player or similar between the volume pot wiper and ground (set the MP3 player volume to zero to start - the chip amp has a lot of gain). Fault or no fault?
If you have clean output from the speaker when driven from an external amp then it looks like the speaker is okay.
If you have the fault when you drive the chip amp from an MP3 player then it does look like the chip amp is damaged (it could still be something else, but that is starting to look unlikely).
If you don't have the fault when the chip amp is driven from an MP3 player then it looks like the preamp stage.
QuoteBut still clean on headphones?
yes
QuoteWas the AC-30 speaker test with the headphone switch contact bridged by wire?
yes
QuoteTo test the Pignose speaker, disconnect it from the Pignose amp and drive it (gently) from the AC-30 output - fault or no fault?
no fault
I found out...
When headphone is plugged in and contact bridged by wire to the ac-30 speakers, signal is clean at the cabinet as it should be and clean on the headphone.
I will check that with the speaker inside the nose.
Yes with headphone and Pignose Speaker no faults.
hm...
Contactspray didn't solve the prob.
The C and R at the Phonejack is not the problem, cause they have just the function to divide the output-signal. 1:10
When i am right, the C 14 & R 10 is a simple LowPass. I will lift them up to see what happens.
Oh much more distortion.
Maybe the C15 0,47µF 50V is the prob?
Oh what is that???
There is no C15 in the board. There is no place for it...
:duh
That was the Prob...
A missing C 15 was it.
I put in a 1µF instead of .47µF that solved the Problem no more distortion. cool!
Thank you all, haha. :dbtu:
The Blue One is the New One! :tu:
Ready to Rock...
Very nice ... although it needs a shave :lmao:
Please please we need a couple pictures from behind showing how it's mounted and how the batteries fit.
Thanks.
PS: obviously it was oscillating, and that .47uF to ground *was* necessary.
In fact , they skimped on the Zobel network, they needed one on each output tey used only one, hot to hot out.
Maybe it worked without, but on the edge of oscillation.
Glad you found it.
Sure some more pics. 8|
If you are interested in more let me know what you would like to see.
Maybe i will change the 1µF to .47µF if that is better?
I played now for an hour and there is just a little, little subtile distortion left.
I recognize that when playing more the Bass and darker Tones.
Maybe the batterys are a bit week.
By the way much better than before...
What is also interesting is the schematic of the TDA7240A in the datasheet. (see below)
On the Output-Side are two C's and two R's (2,2 Ohm & 0,22µF).
I am asking myself, if that could be better by changing that in the Pignose...
It would be more symmetrically.
Any suggestens?
The C14 in Pignose schematic goes directly to GND.
There could be a R in series with that.
The CR networks on each side of the speaker are called Zobel networks and they are there to prevent instability/oscillation.
Who knows better about the IC, the manufacturer, or Pignose?
Me? I'd follow the manufacturers datasheet.
Normally an amp would have only one Zobel network from the output to ground, but something that hasn't been mentioned here is that this particular chip is what is called a "bridge" amp, it is actually two output stages arranged internally to go in opposite directions. When one drives its end of the speaker +ve the other one drives its end -ve.
This results in double the voltage swing across the speaker than would be available from a single amplifier, and is used where there is limited voltage available (particularly in cars, or as here with a battery supply) to get more power output from the same voltage (at the expense of twice the current, naturally - no free lunch). Two outputs, two Zobel networks.
The actual values of the C and R in a Zobel are not usually critical and I've seen R's from 10r to 47r and C's from 0.1uF to 0.47uF, but if you stick to the datasheet values you can't go wrong. One little point however is that these should go as directly as possible between each output pin and the chip ground pin to be effective, i.e. don't mount them on the speaker.
You have made my day - not a new chip, but a circuit design error. Well done. Enjoy. :dbtu:
Agree, what Roly said, follow the datasheet, can't go wrong.
Thanks for posting the back pictures..
In this kind of "unusual" amps, besides the schematic itself, it's interesting to see how they solved the space and distribution problem.
I also find it weird that they used 2 x 6V batteries instead of a single 12V one, although clearly it evens out weight distribution.
That's soo cool, the distortion is gone, completely! :dbtu:
A bridged amplifier inside the TDA-Chip and a missing HF-cut.
I am out for work for a week now, but i am thinking to do a modifikation, that i have two inputs like my Vox Escort.
I would like to have in the front one input for my guitar and in the back a second input in paralel for FX or Playback.
So i would need a High Gain and a Low Gain Input.
I will look inside my Vox but if you have ideas or suggestens please let me know.
thanks so far. :tu:
Interesting idea, that chassis cover/battery support plywood base.
The power supply fried on my Hog 20. I found a second hand replacement which is rated 13.8vdc @ 1.7a ... So I tested the voltage and it registered at 17.8 volts. I know that the 1.7a is sufficient as it is over 1500mA, but the higher voltage is my question.
Quote from: geomiklas on August 16, 2014, 04:21:24 PM
The power supply fried on my Hog 20. I found a second hand replacement which is rated 13.8vdc @ 1.7a ... So I tested the voltage and it registered at 17.8 volts. I know that the 1.7a is sufficient as it is over 1500mA, but the higher voltage is my question.
Unloaded (not connected) power supplies will measure higher voltage compared to when the supply is loaded.
Manufacturers usually rate the supply as it is found in a circuit with a load.
To measure higher voltage out of circuit is normal.
I'd say go ahead and use it, but you may want to wait for more experienced members answer. :)
P = E I
13.8 * 1.7 = 23.5 watts
{assuming you don't have a junk bin well stocked with power resistors...}
The sort of thing I'd do if I wanted to be sure is take something like a car dome light bulb, 12 volt, low power, or 20W QI/downlight, and rig it up with a voltmeter and run it for a couple of seconds while you read the voltage under load. Should put your mind at rest (...or not).
Make sure it has the correct polarity at the connector. This is critical as the wrong polarity will damage the amplifier.
Bumping an old thread cuz I got one of these to repair.
The other guitar player in our band has one of these amps (He goes out busking sometimes)
and he complained about the "fizzy" note decay sound, except he called it a "hum/fuzz".
I actually remembered this thread and told him I could fix it.
As shown in post #19 above.
I added the two Zobel networks on each speaker output of the chip, pins 5 and 7.
.22 cap and 2.7 ohm R to ground as close to the chip as possible. (I didn't have a 2.2 ohm R)
Fixed!
All fizzyness gone!
I love this forum!
Makes me look like a hero! :) ..........but I'm really just a hack with a soldering iron......... ::)
While I was in there I cleaned up some wiring and added a speaker jack
so he can unplug the stock internal speaker and plug in his 4X12 cab.
That should make some noise!
I already tried it with a single 12" Eminence Legend and it sounds great!
Here's some pix of the Zobel net I installed and the speaker jack.
The data sheet pdf for the TDA7240A has a handy chart on page 4
that tells you what the external parts do.
Very handy. :)
I noticed that this amp has waaaay too much bass response for the 6" speaker and makes it "fart" on low notes.
So I reduced the cap on pin 1 of the chip down to 1uf. C13 10uf on the schematic.
Much better.
While I was in there I didn't like the "Squeal" distortion sound.
Way too "over the top" and harsh.
I removed the 4 1N914 clipping diodes D1,2,3,4 and put in 2 red LED's and 1 green and 1 yellow in their place.
Again, much better. The distortion sound is actually usable now.
I also put a 1uf film cap in place of the stock C10 2.2uf electro.
Again, less bass with that change.
re; the zobel network, The stock amp has R10 and C14, removed those since I put the 2R7 resistors and 220nf caps in.
Schematic shows C15 but it was never installed.
Here's the schematic etc for reference.