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Messages - Bajaguy

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1
Amplifier Discussion / Re: TDA2030 amp
« on: July 28, 2014, 11:40:20 AM »
One thing to keep in mind when you are matching a preamp to a chip amp is matching the input impedance of the chip and the output impedance of the preamp. Not paying attention to this will cause some nasty oscillations...... ask me how I know. :grr

 Baja

2
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: April 23, 2014, 04:51:49 PM »
That's a hell of a cool link! I'm thinking that could fit the bill nicely for this amp.....


 Thanks Roly!

 Baja

3
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: April 22, 2014, 07:06:13 PM »
I got some time to play with this last weekend, and did some sketching on the schematic. AFter doing some research on the web, I have a couple of questions before I procede to dump some time and money into this. It seems that the 50EH5 is not a great little tube, and most of what I found while poking around was suggestions to replace it with something bigger and revamp the amp rather than buying an isolation transformer and keeping it in fairly stock trim. There was alot of people that complained about these amps being horrible hum monsters, and after seeing what I've got in the guts of this little guy I can see what they are talking about. Lead dress is horrible at best, and the fact that it was half wave rectified makes me wonder if it's even worth bothering with.

 I know there's a bunch of guys on here that know tubes and have probably played with these enough to offer a solid opinion on this, so I'd really love some feedback on this before I procede any further.

 Thanks ahead,

 Baja

4
Amplifier Discussion / Re: My first Orange Amp - cant even get it open
« on: October 22, 2013, 11:27:02 AM »
On many of the smaller practice amplifiers the handle screws are attached to the chassis, so removal of the handle is required to remove the cabinet. It is very common that the tolex is so tight that the metal chassis will have to be gently persuaded out. Be very carefull, Tolex can be a bear to repair/replace if you mess it up.

 Usually the 60Hz tone is a big sign that the output device is toast. The last amp I fixed that showed that fault was outputing almost 40 volts DC to the speaker, so make sure that the speaker is unharmed before you put it all back together.

 You have some great advice from some of the best techs availible on the net, so be sure to follow thier advice and you'll be well on your way to a working amplifier.

 Best of luck,

 Baja

5
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: August 19, 2013, 05:48:55 PM »
Yea, that's the problem with cell pictures, it's just not a camera. I'll try to take some better pictures of the setup it currently has and add a few values here and there.

 Baja

6
The Newcomer's Forum / Re: New Guy with an interesting design idea
« on: August 19, 2013, 05:46:58 PM »
That's great, I'll get to bread boarding it while I have some down time in the shop this week. I'm really excited to see if this works out! Stay Tuned...

 Baja

7
The Newcomer's Forum / Re: New Guy with an interesting design idea
« on: August 16, 2013, 06:28:49 PM »
Hey Roly,

 Will 2n3904 be ok to replace the BC549C? I'm having trouble sourcing them locally, but I have a hand full of 3904's at my disposal and a weekend off to play with this! :dbtu:

 Baja

8
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: August 16, 2013, 10:35:46 AM »
I haven't been able to find any information on this amplifier anywhere. Looking through the web has been a bust, and even my local tube guru was stumped with this one. I'd be happy to take some more gut shots if anyone would like to see anything else, just let me know.

 Baja

9
  Got it all stuffed together last night and it works like a champ! I'm realy suprised at the fantastic tone from this little amp, it is quite amazing considering it's size.
   I just wanted to take a quick second and thank everyone who helped out with the troubleshooting of this. I know it's quite an undertaking to fix an amplifier that we can't find a schematic for, but with all of your help this was a great sucess and I appriciate it greatly!

 Baja

10
Ok, I got the new chip in this morning just before I had to leave for the job. I had time to solder it in and power it up before I left. I checked the voltage rails and the chip output and all looks good :dbtu:

 I'll stuff it back together tonight and try it with the speaker and report back when I've got tunes....

 Baja

11
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: August 02, 2013, 03:33:13 PM »
Yea, it seems kind of a shame not to at least fire it back up and put those 50EH5's to work before I do something different. I pulled a couple of single ended schematics from various spots on the web, so I'll find a PT that will work and see if I can make something happen.

 Baja

12
Tubes and Hybrids / Re: Another cool but dangerous antique
« on: August 01, 2013, 12:43:07 PM »

Somebody has obviously already spent some time re-capping this one, but they were starting at the wrong end - the front panel should be marked "Off, On/Incinerate".   :trouble

 No kidding there! I've been looking through a couple of old schematics on some of the tube radio sites trying to get a few ideas on which direction to go. There's some really good single end schematics for the 50EH5's, but I've been looking around for a push pull for them and nobody seems to have anything close.

 Maybe it's destined for a TDA2003 with a good preamp. Ya think anyone would look inside to see if it is still a tube amp :duh

 Baja

13
Tubes and Hybrids / Another cool but dangerous antique
« on: July 30, 2013, 05:27:05 PM »
Last night I went to a local swap meet and poked around for a couple of hours. I ran across a guy that had a couple of old guitars on his table, and after talking to him for a bit was given this old tube amp. Yea, it's one of the old line voltage man killers everyone talks about (series chained heaters, hot chassis, no transformers of any kind, etc.). I tried looking it up and found no reference to it at all on the web. It's in poor shape, more than likely not worth anything, and free (still my favorite part of any amp project :tu:)

 The two drivers are 50EH5 and for some reason somebody stuck an EL84 in where the preamp goes.... The good thing is all of the tubes tested good :dbtu:

 I'm still trying to decide what I want to do with it, mabey a hybrid with a couple of 12ax7's and a nice 15 to 20 watts of chipamp goodness......

 Just thought you'd enjoy the pictures!











 Baja

14
The old chip had the isolation washer and the screw cover, so it sounds like either one will work.

 I checked the speaker last night and all is well. Thanks again for all the help!

 Baja

15
I just got on Mouser and TI (who bought out National in 2013) lists 2 different chips for the 3886T, one in a package that I don't recognize. I went ahead and ordered both, any idea what the difference is? They list a TO-220 11 and a PFM-11.

 Baja

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