I found this post on another thread about the Hammond iron. Maybe yours ran too hot or was defective. You may want to reach out to this forum member:
Join Date: Dec 2016
Location: Denver, CO
Default Tubelab SEII Chassis
"So I was planning on posting a whole set of - how I built my SE II and got all lazy but thought folks might find this useful.
I had trouble with Hammond 276 and 376X power transformers running REALLY hot so ended up going to a B373EX which is HUGE, but runs really cool. Used Edcors for outputs and mil-spec Vishay-Dale resistors (Mouser) or matched ones from Sonicraft."
Join Date: Dec 2016
Location: Denver, CO
Default Tubelab SEII Chassis
"So I was planning on posting a whole set of - how I built my SE II and got all lazy but thought folks might find this useful.
I had trouble with Hammond 276 and 376X power transformers running REALLY hot so ended up going to a B373EX which is HUGE, but runs really cool. Used Edcors for outputs and mil-spec Vishay-Dale resistors (Mouser) or matched ones from Sonicraft."
Thanks. I have read that elsewhere - specifically that the 374BX is far superior to the 274BX (runs far cooler, etc.).
One thing I have realized is that the chassis holes for the transformer would have to be re-drilled, but I guess that's okay as long as the new transformer is larger.
I am quite disappointed that I only got 3 days (or so) out of this transformer. It makes me wonder why they would even build a product so weak.
On the other hand, upgrading or changing to another manufacturer means writing off the money spent on the 274BX and spending more money to get the new one. I already have close to $800 into this amp (maybe more at this point, as I have lost track).
If I can get a replacement 274BX from Hammond, I am thinking that'll have to be the solution, despite me not really wanting the damned thing in my amp.
One thing I have realized is that the chassis holes for the transformer would have to be re-drilled, but I guess that's okay as long as the new transformer is larger.
I am quite disappointed that I only got 3 days (or so) out of this transformer. It makes me wonder why they would even build a product so weak.
On the other hand, upgrading or changing to another manufacturer means writing off the money spent on the 274BX and spending more money to get the new one. I already have close to $800 into this amp (maybe more at this point, as I have lost track).
If I can get a replacement 274BX from Hammond, I am thinking that'll have to be the solution, despite me not really wanting the damned thing in my amp.
Last edited:
Last edited:
Put your DMM on lowest resistance setting. Touch probes together. Probably you will get around 0.3 ohms. Now test the transformer wires. Then touch probes again to confirm. This is with all the transformer wires removed from board.
If stuck probably you can just run the amp with the SS rectifiers as long as there is no short between any of the red wires and the green or yellow. Remove the rectifier tube; do not connect the yellow wires; install jumper for SS operation; make sure you have the correct SS diodes installed (1200v should work but 1500v is better). The CL90 will slow down turn on voltage. You may have to increase the cathode resistors as shown at the Tubelab site; especially for EL34's (SS diodes give higher voltage).
I have the Hammond 374BX in my SSE and it works fine. The extra $$'s seems worth it over the 200 series. Also, I highly doubt there is a significant difference between Hammond and Edcor. I have purchased lots of Hammond power and output transformers with no problems.
If stuck probably you can just run the amp with the SS rectifiers as long as there is no short between any of the red wires and the green or yellow. Remove the rectifier tube; do not connect the yellow wires; install jumper for SS operation; make sure you have the correct SS diodes installed (1200v should work but 1500v is better). The CL90 will slow down turn on voltage. You may have to increase the cathode resistors as shown at the Tubelab site; especially for EL34's (SS diodes give higher voltage).
I have the Hammond 374BX in my SSE and it works fine. The extra $$'s seems worth it over the 200 series. Also, I highly doubt there is a significant difference between Hammond and Edcor. I have purchased lots of Hammond power and output transformers with no problems.
There may be a tube amp DIY aficionado in Kamloops who could help you out. You might want to check on Craig's list. If the amp ran perfectly for several hours then went into smoke mode I tend to think there is a faulty part somewhere in the circuit, not an improperly soldered board or incorrectly placed part. If your filter cap went bad and you replaced it, and things still were not right, I would be thinking the problem would likely be in the circuit prior to that cap, which leaves the iron and rectification stages. Heater wires perhaps but I don't think likely. You could of course go with solid state rectification and bypass on the tube rectifier circuit and see if that works.
Cogitech has measured something other than infinity between the green and yellow wires more than once. Regardless of what the reading is, the transformer has problems.
Very highly unlikely. In order to damage a transformer some serious current or voltage must be applied to it in an incorrect manner, or it would have to been overheated severely for an extended period of time. Your amp was making music when it died. There was no serious fault current flowing or else the music would have at least been very distorted.
I would be curious myself, but I also wouldn't give Hammond any excuse to avoid sending you a new transformer. If they offer to look at the transformer, send it to them. Lead them to this forum thread if they are willing to read it. It gives a pretty thorough look at all the troubleshooting that went on, and the time frame, including frustration related delays. In reality your transformer died in the first few days of use. That's when a "manufacturing defect" will usually manifest itself.
I started using Allied Electronics' house branded power transformers back in the 70's when I was making guitar amps. They were, and still are made by Hammond. I have had exactly one fail in all that time and it was about two years old in the very first TSE ever built. Autopsy revealed that it was rusty and still wet inside. It had gotten very wet when Hurricane Wilma (2005) filled my lab with rainwater. The transformer played on for about two months after the storm before blowing the line fuse.....of course I did the first thing that came to mind, I stuck a 10 amp fuse in there and plugged it in. The amp played for a while before smoke started coming out of the transformer. I put in another and it still plays today.
It wasn't the filter cap that failed. The heater circuit in the SSE is elevated to about 30 volts to reduce hum. This voltage is derived from a voltage divider off main B+. There is a 10K resistor and a cap in parallel from the 6.3 volt winding to ground, and a 150K to B+. The cap can vary depending on the build but I usually use a .22 to .47 uF at about 100 to 250 volts depending on what I have at build time. It is that bypass cap that failed. It didn't just die, it smoked indicating a fairly large current flow. The 150 K 2 or 3 watt resistor could only pass 3 mA or so on a B+ of 450 volts. The resistor was intact and the correct value in the pictures taken after the smoke. No wiring anomalies were noted in the pictures and several simple tests eliminated the usual suspects. So how did over 250 volts get on the heater supply?
A short in the transformer is the only logical explanation, but early testing failed to find one. My guess it that it is transient, and possibly occurs only when the transformer gets warm.
Very highly unlikely. In order to damage a transformer some serious current or voltage must be applied to it in an incorrect manner, or it would have to been overheated severely for an extended period of time. Your amp was making music when it died. There was no serious fault current flowing or else the music would have at least been very distorted.
I would be curious myself, but I also wouldn't give Hammond any excuse to avoid sending you a new transformer. If they offer to look at the transformer, send it to them. Lead them to this forum thread if they are willing to read it. It gives a pretty thorough look at all the troubleshooting that went on, and the time frame, including frustration related delays. In reality your transformer died in the first few days of use. That's when a "manufacturing defect" will usually manifest itself.
I started using Allied Electronics' house branded power transformers back in the 70's when I was making guitar amps. They were, and still are made by Hammond. I have had exactly one fail in all that time and it was about two years old in the very first TSE ever built. Autopsy revealed that it was rusty and still wet inside. It had gotten very wet when Hurricane Wilma (2005) filled my lab with rainwater. The transformer played on for about two months after the storm before blowing the line fuse.....of course I did the first thing that came to mind, I stuck a 10 amp fuse in there and plugged it in. The amp played for a while before smoke started coming out of the transformer. I put in another and it still plays today.
It wasn't the filter cap that failed. The heater circuit in the SSE is elevated to about 30 volts to reduce hum. This voltage is derived from a voltage divider off main B+. There is a 10K resistor and a cap in parallel from the 6.3 volt winding to ground, and a 150K to B+. The cap can vary depending on the build but I usually use a .22 to .47 uF at about 100 to 250 volts depending on what I have at build time. It is that bypass cap that failed. It didn't just die, it smoked indicating a fairly large current flow. The 150 K 2 or 3 watt resistor could only pass 3 mA or so on a B+ of 450 volts. The resistor was intact and the correct value in the pictures taken after the smoke. No wiring anomalies were noted in the pictures and several simple tests eliminated the usual suspects. So how did over 250 volts get on the heater supply?
A short in the transformer is the only logical explanation, but early testing failed to find one. My guess it that it is transient, and possibly occurs only when the transformer gets warm.
Tublelab: You are far more knowledgable and experienced in electronics and all things amplification than I am, and you are this quality and time-honroed circuit's designer. In this case I would have to agree with you. After all the trouble shooting you two have done, I put my money on the transformer. Hammond is a large company and should hopefully take it back. They should exchange it (with cost difference paid) for the higher end model. That way cogitech gets what he wants and is only out another $50. Several years ago I went nuts trying to get a new PC I was building up and running. Hours and hours of work and nothing. I finally determined it had to be the mother board. It was, and they replace the faulty board. Fired right up.
It all depends on the company, and the luck of the draw with who you get on the other end of the phone line.
I bought a high end core i7 ASUS laptop in 2014 and it never really worked right, but I needed it since my career had just came to an abrupt end, and was in the process of moving everything I owned 1200 miles on short notice. The intermittent behavior kept getting worse, and after about a year I called the phone number on the box for an RMA. The box that the computer came in clearly stated "two year rapid replacement warranty" with a phone number.
I called the number and gave the woman the details and she replied that my computer only had a 1 year warranty which had just expired. This was verified by a code number on the bottom of the computer itself. She explained that it didn't matter what the box said, it's what's on the computer itself that counted. I tried several other calls, emails with pictures of the box, all went unanswered. I haven't bought an ASUS product since, and likely never will. My new laptop is an MSI and so are most of the motherboards that I buy.
I kept using that POS for a few years until some of the keys on the keyboard went out. One day I decided to rip into the ASUS before tossing it into the trash. There were two obvious manufacturing defects both easily cured with a bit of ordinary masking tape. There was a flex circuit from the keyboard to the motherboard that ran under the hard drive, and another flex circuit from the track pad that ran near the hard drive. The laser cut drive bracket with razor sharp edges had cut into both of those circuits causing random button and key presses, eventually severing some traces on the keyboard flex. I got a new keyboard for $20 on Amazon with the flex. That and some tape fixed the shorting, and the old laptop is actually useful now.
I bought a high end core i7 ASUS laptop in 2014 and it never really worked right, but I needed it since my career had just came to an abrupt end, and was in the process of moving everything I owned 1200 miles on short notice. The intermittent behavior kept getting worse, and after about a year I called the phone number on the box for an RMA. The box that the computer came in clearly stated "two year rapid replacement warranty" with a phone number.
I called the number and gave the woman the details and she replied that my computer only had a 1 year warranty which had just expired. This was verified by a code number on the bottom of the computer itself. She explained that it didn't matter what the box said, it's what's on the computer itself that counted. I tried several other calls, emails with pictures of the box, all went unanswered. I haven't bought an ASUS product since, and likely never will. My new laptop is an MSI and so are most of the motherboards that I buy.
I kept using that POS for a few years until some of the keys on the keyboard went out. One day I decided to rip into the ASUS before tossing it into the trash. There were two obvious manufacturing defects both easily cured with a bit of ordinary masking tape. There was a flex circuit from the keyboard to the motherboard that ran under the hard drive, and another flex circuit from the track pad that ran near the hard drive. The laser cut drive bracket with razor sharp edges had cut into both of those circuits causing random button and key presses, eventually severing some traces on the keyboard flex. I got a new keyboard for $20 on Amazon with the flex. That and some tape fixed the shorting, and the old laptop is actually useful now.
Yes, in days of old I purchased a 42" HP plasma TV for $2,000, when those models were the bomb. 720p. Weighted a ton. After a few months (past 90 day warranty) the TV had red pixel sparkles in it. This was a common problem in the on line forums. I made tons of calls and got nothing but crap. One night in the wee hours I got an 800 number person who was kind and we kind of hit it off. He said he would have a tech visit my house. Two or three weeks later a tech showed up, pulled off the back of the unit and replaced one of the circuit boards. Problem fixed. No charge Worked like a charm after that. Of course not many years later 1080p was the bomb, and one could get a set for far cheaper. Today plasma is long gone, and you can grab a 55" TV at Costco for less than $500. Persistence pays off.
Last edited:
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.