Try disconnecting the phantom supply completely, not just switching it off with the Phantom "On/Off" switch. Make sure your other supply rails are at the correct voltage.

Put a 400Hz sine wave into the inputs & check down the signal path after each stage to hear where the pre is distorting.

Peter

Hey Peter,

I think I can figure out how to disconnect the phantom power supply; and can measure the voltages at the other supply spots ?rails?; but I'm really not sure what you mean when you say to "Put a 400Hz sine wave into the inputs & check down the signal path after each stage to hear where the pre is distorting."

How would I generate the sine wave and how do I "put" it into the signal path? Do I record a 400Hz sound and then play it into my mic? Also, where do I check, and with what?

Temporarily lost in electronic space.......Mark

To disable the phantom, there should be 2 x 6k8 resistors connecting the 48v supply to the input pins. Lift one end of each of these.

quote:

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How would I generate the sine wave and how do I "put" it into the signal path? Do I record a 400Hz sound and then play it into my mic? Also, where do I check, and with what?

---

What I meant was to connect a signal directly to the input of the mic pre, ni mic involved. Then check the signal thru the preamp using the method described here :

http://recording.org/users/kev/signaltracing.htm

Check for level loss.
Peter

Back on the electronic path again thanks to you Peter. Thanks for the link. Thats a very cool site that I didn't know about.
Also, your site has a multitude of great DIY projects. I've browsed around there a few times before, but didn't make the connection with you.
Obviously I have a lot to learn, and really appreciate the expertise that is being offered here.
Later.....Mark

OK--- that took longer than expected since I kept getting interupted by "work" (Dobie Gillis) and other sh_t but...

I finally built one of the signal testers. When I plug a drum machine into the DI of each channel and touch the probe to the front two connections of the PAD switch, I CAN HEAR IT playing in my little practice amp. So, I guess the DI works.

Now however,I'm having trouble figuring out how to hookup a mic to this contraption and AGAIN I've gotten to the limits of my deductive reasoning power (POWER being the misnomer of the day obviously). Sometimes there are just TOO many wires, and not enough brains around here.

Would it be against the rules to get Peter a schematic so he can be very specific in his suggestions? I know he asked for one back in Janaury and it was mentioned it was only for paying customers. However, he seems to have the most depth of knowledge here and yet he is at a distinct disadvantage when trying to help as he has to work only in generalities.

Mark

I would personally love it if Peter had access to the schematics. He has been a tremendous help on both of these threads. I just want to leave that decision up to Scott.

I know that one of Scott's techs looks at this board periodically so maybe they can give us a definitive answer.


Jason A.

Dear All

I hope waiting for Scott's Tech to appear won't stop Peter, or anyone else, from replying to my last post.

I just got done reading the tube pre thread and laugh and laugh at Peter's comment about his first project done in 1977 "NEVER WORKING". That comment scares me more than the skin crawling 900 volts. I also laughed at the one comment where "the hypercube" tried to avoid saying that he sent the kit back to Scott to finish. I'm getting closer and closer to that eventuality I think.

I'm trying to avoid giving up, since I had the thing working at one point. But it sputtered out on me. In the tube thread M also mentioned that he fried something on his power supply. All you need to do is go back to page 6 of this thread to see where I fried the B30 rectifier AND the transformer. So far I think I have about $2,300 bucks into this project if you count the kit, the replacement parts, the time spent overworking the solder joints at $2/hr., the time reading through the hamptone site at $2/hr, and the reading through of these two threads and trying to dream up relevant question to post here, at say $2/hr.

Until someone comes up with another suggestion, I think I'll start reading through this thread again from the beginning, hoping to catch that one precious comment that will put my project over the edge....I mean put it all together again.

Cheers...Mark

quote:

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Peter's comment about his first project done in 1977 "NEVER WORKING".

---

well, I did use a 100W soldering iron that burnt an inch deep hole in my desk....

I'm getting lost without a schem, if someone from Scott's company is monitoring this thread, I could use it!

Peter

quote:

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Originally posted by Peter Cornell:

quote:

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Peter's comment about his first project done in 1977 "NEVER WORKING".

---

well, I did use a 100W soldering iron that burnt an inch deep hole in my desk....

I'm getting lost without a schem, if someone from Scott's company is monitoring this thread, I could use it!

Peter

---

Peter,

If you email me a mailing address at jasonandamya@yahoo.com I will mail you my copy of the magazine the original article was published in. Like I said before, there have been minor tweeks done but it is essentially the same circuit published in the magazine. It doesn't have near the detail of the kit instructions but maybe it would help.

Thanks for your help.

Jason A.

quote:

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Everything's been going fine, the posts here have been helpful, I've been careful and it all looks great but: When I test the power supply (without the B-50 rectifier(?) installed - only the B-30) I get 26 volts on what should be the 48 volt conductors and a -5 volt reading on what should be the 25.5 volt ones, and the way I read it there shouldn't be any reading on the 48 volt conductors without B-50 installed. I examined everything closely, polarities all seem right, soldering looks good, can't find anything wrong. Any ideas? Thanks to one and all!

---

Yo everybody.....

Thought I'd mention a few things. I just finished building the kit and all went well. Only, I ran into the exact same problem (quoted above) and decided to go ahead and keep building. It all worked out in the end....voltages and all.

Point is, the picture on the site shows a board with B50 installed without B30. I'm guessing B50 should be installed first and tested before adding B30. I hope Scott gets that one worked out on the manual....I can see real beginners jumping off bridges at that point!

On another note....

Did you guys do the DC voltage tests of the 2N5457s at the end? I'm not sure how to do it exactly. Is it important? Everything seems to be nominal. Anybody care to shed som light on how it's done?


Thanks...

heylow

quote:

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Originally posted by heylow:
On another note....

Did you guys do the DC voltage tests of the 2N5457s at the end? I'm not sure how to do it exactly. Is it important? Everything seems to be nominal. Anybody care to shed som light on how it's done?


Thanks...

heylow

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I didn't do it. I was too anxious at that point.


Jason A.

Sounds like a component is not happy, or else the unit is going into oscillation.

Regarding the first option. Once the unit is not happy, feel all the components & see if any are getting hot. If not, do a DC voltage comparison between the 2 channels. This is detailed in this thread or the other Hamptone thread. If there is a difference between the 2 chans, check all the components in that area.

Second situation. Are your Input & Output leads running near each other? Is your input lead shielded (very important)? Does it happen if your input is shorted to ground (make sure phantom is switched off)?

Peter

quote:

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so when you say a component isnt happy do you mean i need to find and replace it?

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'Fraid so. Could be that something is out of spec & needs replacing.

quote:

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replaced the audio taper leads

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Are these the leads to the audio taper pot? If there is one...
If so, measure the pot with your multimeter, & make sure it is not goin open cct.

Regards
Peter

Hey all, this is my first post on this board. I got my HJFP2 together and neither channel works right, but they both do something different. On channel 1 the volume pot goes from nothing to what seems to be max gain in about the first 2 degrees of turning. On channel 2 the gain is extremely low. Any ideas? I checked the orientations of the transistors and they're all following the diagram for the main PCB correctly. The voltages coming off the power supply seemed reasonable before soldering to the channel boards. Is there a way to check voltages now without disassembling?

quote:

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Originally posted by Aaron:
Hey all, this is my first post on this board. I got my HJFP2 together and neither channel works right, but they both do something different. On channel 1 the volume pot goes from nothing to what seems to be max gain in about the first 2 degrees of turning. On channel 2 the gain is extremely low. Any ideas? I checked the orientations of the transistors and they're all following the diagram for the main PCB correctly. The voltages coming off the power supply seemed reasonable before soldering to the channel boards. Is there a way to check voltages now without disassembling?

---

On the one with high gain, check the wiring to the pot. I had the same problem and I had the wiring right on the board but had the send and return switched around on the pot.

Just a thought


Jason A.

Thanks for the response! If you're looking at the pot with the shaft pointed towards you and the feet pointing down, I've got the leftmost tab going to the 2 grounds, the tab on the right going to the spot with the + on it in the picture of the board (snd, I thought), and the middle tab going to the last spot left. I've got both channels done that same way. One strange thing I did notice while putting the input transformers in was that one transformer had a wire soldered from one pin to the can. The other input transformer didn't have that, and I don't really know if it maybe it was supposed to? The channel that goes straight to full blast has the transformer with the wire.

Aaron-

Make sure you go to the Hamptone site and read the tech updates for the HVTP2. Scott posted this latest update last month and talks about the Mogami wire getting overheated and the connection compromised. Also, if the tabs on the pots were stressed at all, this too could cause a problem.

Keep at it...

-Steve

Alright, I'm dumb. It WAS the pot. I had the connections mixed up in my head when I soldered them in, and then still didn't notice even after I checked again. Everything works great now on both channels! Thanks for the help! I can't wait to get some mileage out of it.

Well, I did it. I purchased the HJFP2 kit, put it together and used it. All within a week. I found the kit's instructions to be very well written and the cheat-sheets were a great help, too. The only time I ran into a problem was when one of the LEDs burnt out, giving some strange readings around the +48v switch. Putting a fresh $.50 LED in fixed the problem and made me a happy guy. I highly encourage anyone on the fence about ordering this kit to go for it. My schematic reading skills are fairly poor, but Scott made it so I didn't have to put them to the test much. Great fun.

-Cory

I have enjoyed mine since last Spring - it's a great piece of kit.

I have now purchased the step-gain attenuator kit. Put it together and installed this AM. They are very solid switches and as far as I can tell are amazingly precise. I have no concerns about future stereo recordings done with my Hamptone. They are 23 step in 2db increments.