S-harp
25 posts
May 19, 2012
8:34 AM
|
Searching info about the Harptone but can't find anything.
Any thoughts? And what is it fastened on the back of the speaker?
Under the hood we find 6SJ7, 6J5 GT/G and 2x 6V6 S
Front:
Wireing:
Logo:
The sound coming out of this little gem is sweet. It likes all microphones. The bottom end is awesome for what I guess is 5W and the highs are creamy.
----------
The tone, the tone ... and the tone.
Last Edited by on May 19, 2012 8:39 AM
|
5F6H
1204 posts
May 19, 2012
9:52 AM
|
2x6V6? Are you sure that the tube under the speaker isn't a 5Y3 rectifier? Red wire from the outpur transformer (the thing bolted to the back of the speaker) only seems to run to one tube, which would be the power tube - 6V6). Only 2 primaries on the power transformer show that the amp is single-ended, like a champ/VHT Special 6, so yes ~5W-ish seems about right.
What does the writing say on the rectangular metal object behind the preamp tubes?
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
isaacullah
1959 posts
May 19, 2012
10:09 AM
|
Looks like the capacitors have all been replaced. Did you do that yourself? Were the original caps the old rolled paper caps?
----------
== I S A A C ==
View my videos on YouTube!
Visit my reverb nation page!
|
S-harp
26 posts
May 19, 2012
10:10 AM
|
Yes. 5Y3 GT it is ... tells you what I know 'bout amps (-:
I'll check the writing ... it's hard to see ....
----------
The tone, the tone ... and the tone.
Last Edited by on May 19, 2012 10:45 AM
|
S-harp
27 posts
May 19, 2012
10:43 AM
|
@isaacullah... I haven't done any work on the amp. It was like this when I found it.
@5F6H ... You mean this one?
rectangular metal object:
----------
The tone, the tone ... and the tone.
Last Edited by on May 19, 2012 10:43 AM
|
5F6H
1205 posts
May 19, 2012
10:49 AM
|
"2x25MFD 25WVDC" cathode bypass caps for the preamp tubes. It's a cap can.
That's a much better shot, can see the tube orientation now.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
isaacullah
1960 posts
May 19, 2012
12:02 PM
|
Ahh, yes, I see in your new picture that there are still couple of old rolled paper caps left in there... The orange film caps (maybe tantalium?) and the blue and black can caps are new... The blue and black can caps are the power supply filtering caps and the orange ones are likely serve various decoupling and drop functions. It's good that they've been replaced... I was mainly curious if you'd done it yourself, cause it looks like whoever did it did a very nice job of it! ;)
----------
== I S A A C ==
View my videos on YouTube!
Visit my reverb nation page!
Last Edited by on May 19, 2012 12:03 PM
|
5F6H
1206 posts
May 19, 2012
12:11 PM
|
All the visible caps look to have been changed, only appear to be a couple of original resistors. Not necessarily a bad thing.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
S-harp
28 posts
May 19, 2012
12:27 PM
|
Thanks for your answers.
Obviously, I don't know much about the insides, just what sounds great or not.
As I understand, there has been some caps replacements. Still, there is some humming going on. Any thoughts?
----------
The tone, the tone ... and the tone.
|
5F6H
1207 posts
May 19, 2012
12:47 PM
|
Can you live with the hum? Single-ended amps aren't as good at hum cancelling from the heaters as push-pull amps, lots of old single output tube amps hum.
There are fixes but likely to be very labour intensive with your amp, as they mean rewiring the filaments to all the tubes....which in turn means a lot of regrounding.
If it doesn't interfere with the tone when you are playing, I'd say quit while you are ahead.
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
S-harp
29 posts
May 19, 2012
1:33 PM
|
No, when playing it's good. Tnx for your input.
----------
The tone, the tone ... and the tone.
|
MJ
420 posts
May 20, 2012
2:25 PM
|
I may be wrong but it looks like a field coil speaker .
|
S-harp
30 posts
May 20, 2012
3:04 PM
|
@MJ ... Field coil speaker ... hope that's a good thing (-:
I like how it sounds though ... Is that a speaker type or brand?
Have you heard about this amp before? Harptone...
I'm curious about it ... Is it à known amp label? I haven't found any info ...
----------
The tone, the tone ... and the tone.
Last Edited by on May 20, 2012 3:05 PM
|
5F6H
1208 posts
May 20, 2012
3:28 PM
|
It's a regular, permanent magnet speaker, it just has the output transformer bolted to the frame. This was quite common in the 50's.
A field coil speaker is a more complicated thing to change if it fails... permanent magnet speaker can be changed with nut drivers & a soldering iron.
S-Harp, you have everything in front of you to possibly know about this amp...you may well have more information than all but the guy who designed it!
Your amp is...
Single ended 6V6, running in cathode bias.
5Y3 rectified.
It has 2 channels, a "pentode" 6SJ7 channel and a "triode" 6J5 channel. Have you noticed a preference?
It must run very low voltages to survive having a 200ohm cathode resistor.
It has a smoothing choke between the rectifier and the output transformer (like a 5E1 champ).
I can't see any evidence of a negative feedback loop. Fenders nearly always had these but most other manufacturers did without.
If you were really bored one day you might make a chart of the tube sockets and make a note of which components run from which pin, to another?
----------
www.myspace.com/markburness
http://www.facebook.com/markburness
|
S-harp
31 posts
May 20, 2012
3:56 PM
|
F56H ... "It has 2 channels, a "pentode" 6SJ7 channel and a "triode" 6J5 channel. Have you noticed a preference?"
What I have noticed is that there is à difference in tone, or maybe more precise in the action. I didn't know the channels were different. Another thing is when running through one channel the other channel interacts and turning up its volume rounds off the tone, smears it out ... I don't know if the term sag is correct, compression perhaps, but something happens ... and that also kills feedback when playing loud, not that feedback is à problem with this amp.
----------
The tone, the tone ... and the tone.
|
