I have an ampex 2010 suitcase amp that worked until one day it got real noisey with lots of static so I shut it off and decided to recap it. I replaced the power supply caps and the noise is still present even with just the rectifier in it. I used a dim bulb tester and I don't think there is any shorts because a 40w bulb does not glow. What is my amps ailment?
correct me if I am wrong but I thought that if the output tubes were removed then it would not matter if there was DC passing to pin 5. I know in tube amps the speaker should always be hooked up when on but what about if the output tubes are removed? I would like to check voltages but the noise is so bad with the speaker hooked up it is pretty much impossible.
http://recordist.com/ampex/schematics/612man/ampex612.jpg
http://recordist.com/ampex/schematics/612man/ampex612.jpg
Last edited:
That was surely going to be my suggestion! With no output tube in place, but the rectifier in place, any noise from the speaker must be from an arcing (to ground) output transformer. You will want to make sure that the transformer matches the application (i.e. SE or PP), has the proper primary impedance, secondary impedance, and that it is rated for the power output rating of the amplifier.
Dave
Dave
Well I was putting the amp back together and noticed that where the line power comes into the amp the common wire had broken off so only the hot was connected to the amp. I soldered it back on and the problem has been resolved. What are the chances I did some serious damage to the output transformer?
The reading of 150 ohms is about normal. The reading of 8.3K is not. Do not operate the amplifier in this condition. I don't know what output tubes you are using, other than since the plate connections are on pin #3 it sounds like a standard octal tube. In any event, operating any output tube with no plate voltage while the screen grid does receive power will damage the tube. Also, the other output tube will be under biased if a common cathode bias resistor scheme is used. There is little doubt that the output transformer needs to be replaced.
Dave
Dave
It has 6v6 output tubes. After I resoldered the wire I turned it on without the 6v6's in. I checked voltage at the plates and screens and both tubes were the same. I have two of these amps and I was checking resistances of the other amp's tranny and it was 150 on one side and an open line on the other. I also can't read through from pin 3 to pin 3. A friend of mine got them for free and told me he would give me one if I fixed them up. When he gave them to me I turned them on with a dim bulb tester and they both worked except they were real noisy. After a few minutes of playing guitar through one the amp made bad noises and the 100w bulb lit right up so I shut it right off. I replaced the power filter caps for the one that crapped out. This is where I am at right now, if the other tranny is bad too this is not going to be good.
I'm sorry to say it doesn't sound good. If these are classic amplifiers with push-pull 6V6s, each primary half of the output transformer (i.e. from the B+ lead to either plate lead) will likely read around 125-175 ohms, and about 250-350 ohms from plate to plate. If one winding is open, or has a very high resistance, it is very possible for the amplifier to "work" (for a little bit anyway), but it won't deliver anywhere near it's designed performance, and as mentioned in my last post, it would also be very hard on the tubes to operate the amplifier like this. If both output transformers are bad, that is probably why your friend got the amplifiers so cheap! The good news is that there are plenty of general replacement transformers available for this type of application, so if all else is serviceable or the amplifiers are otherwise worth the effort, then they can certainly be fixed.
Dave
Dave
I am going to look into it more tomorrow. One of the amps had a bad speaker connection so maybe that stressed the OT.Also, I am afraid when I was playing through one of the amps a section of the multi cap shorted and the OT took a hit. The one with the bad speaker connection sounded terrible, and the one that was just a little hummy crapped out when I hit a big E chord.
If the amp was running wide open with no load, that is a recipe for disaster in a guitar amp regarding the output transformer. In the other amp, if a can cap shorted out, that would do nothing to the output transformer, but the power transformer would certainly not like it.
Wavebourn suggested one of the output transformer leads may have simply come lose -- is that the case? Or has it burned away from its winding connection?
Dave
Wavebourn suggested one of the output transformer leads may have simply come lose -- is that the case? Or has it burned away from its winding connection?
Dave
I don't think Dave it is the only problem. Open wire with no current would not cause noise. Looks like there is either some moisture, or trace of electric spark, in the transformer or on the tube socket.
Hey, FWIW, I think that transformer may have been made by V&F Transformer in Bartlett, Illinois?
I have a bunch (to use the term lightly) of Heathkit power transformers and they have an 'EIA manufacturer's code' on them. 60 and 549 were among the most common.
I interpret 606013 to mean 13th week of 1960, coincidental that the EIA code preceding the date code happens to be 60, for V&F Transformer.
For example, 5496013 would be on it if vendor 549 had manufactured the transformer. 549 was formerly know as Midwest Transformer, another Illinois transformer manufacturer (maybe near Grays' Lake, Illinois?), but they merged with someone else and I have no idea who they became, if anyone.
Before anyone asks me about any other codes, that just exhausted 99.5% of my EIA code knowledge. Grand Transformer had two different codes because they had in addition to their primary facility in Grand Haven MI another facility closer to Benton Harbor, MI (I don't remember what city it was) with a 2nd code.
Hmmm, there was also a "Magnetic Windings Co." out east, in the Allentown, PA vicinity, or New Jersey across the border. All I can remember are vague associations between the company and nearby two cities.
Heyboer is still in business too. I didn't see enough of their stuff to recognize the number.
I tried to inquire of the EIA once, maybe in the '90's, and a unified and complete list of such codes. I couldn't even reach anyone there who had any idea what I was talking about. They offered me other weird unrelated 'standards' stuff with unpleasant fees. I don't think understanding a vendor ID system they probably established constitutes a standard that costs justifies maintenance fees. It might take knowing who to contact with the knowledge rather than 'tunneling' thru the switchboard. Or it's so obsolete they don't have a reason to keep track of it....but there was an EIAJ, too...
I have a bunch (to use the term lightly) of Heathkit power transformers and they have an 'EIA manufacturer's code' on them. 60 and 549 were among the most common.
I interpret 606013 to mean 13th week of 1960, coincidental that the EIA code preceding the date code happens to be 60, for V&F Transformer.
For example, 5496013 would be on it if vendor 549 had manufactured the transformer. 549 was formerly know as Midwest Transformer, another Illinois transformer manufacturer (maybe near Grays' Lake, Illinois?), but they merged with someone else and I have no idea who they became, if anyone.
Before anyone asks me about any other codes, that just exhausted 99.5% of my EIA code knowledge. Grand Transformer had two different codes because they had in addition to their primary facility in Grand Haven MI another facility closer to Benton Harbor, MI (I don't remember what city it was) with a 2nd code.
Hmmm, there was also a "Magnetic Windings Co." out east, in the Allentown, PA vicinity, or New Jersey across the border. All I can remember are vague associations between the company and nearby two cities.
Heyboer is still in business too. I didn't see enough of their stuff to recognize the number.
I tried to inquire of the EIA once, maybe in the '90's, and a unified and complete list of such codes. I couldn't even reach anyone there who had any idea what I was talking about. They offered me other weird unrelated 'standards' stuff with unpleasant fees. I don't think understanding a vendor ID system they probably established constitutes a standard that costs justifies maintenance fees. It might take knowing who to contact with the knowledge rather than 'tunneling' thru the switchboard. Or it's so obsolete they don't have a reason to keep track of it....but there was an EIAJ, too...
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.