Eico HF-22's total reassembly.
- Thread starter marloubow
- Start date
yes that is where I would put it, you may want to considering putting a CL-90 on each leg of the A/C in ( Kegger recommended that to me), ...remember it gets quite hot so place it carefully.
Cheers,
Kirk
Cheers,
Kirk
Martin I think your drawing confused me ( the lined circles are not the CL-90's??)...you may want to seek advice from someone else before installing. I've only installed a few of these, but all you need to do is put one on one of the A/C legs before the PT
hope that helps.
cheers,
Kirk
hope that helps.
cheers,
Kirk
shelby1420
Enjoying the music.....
Brilliant work!!!!!
bhamham
Super Member
That's how I did my Sansui 1000A on each leg of the A/C in. They go in series so lift the wire to connect one end of the thermistor and the other end to the fuse contact. You could do the other to the first A/C outlet. Maybe there's room to mount a small tag strip? Kirk's right, they get hot so allow room around them. Good idea to replace the death cap circled.
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bhamham
Super Member
Hi Dandy,
The thermistors are used as an 'inrush current limiter'. They provide a high resistance at turn on which lowers as they heat up. The idea being to reduce any immediate damage to components.
I probably wouldn't use them with a GZ34/5AR4 and not sure about the 5U4 but works well with my Sansui which is SS rectification.
The thermistors are used as an 'inrush current limiter'. They provide a high resistance at turn on which lowers as they heat up. The idea being to reduce any immediate damage to components.
I probably wouldn't use them with a GZ34/5AR4 and not sure about the 5U4 but works well with my Sansui which is SS rectification.
Dandy
Addicted Member
Thanks Bruce, that confirms my understanding that their use here is because the 5U4 doesn't have the slow warm up of the 5AR4.
If I may -- from the standpoint of limiting current, inrush limiters provide only a limited benefit when any type of vacuum tube rectifier is used. Even when a directly heated type is used (such as the 5U4), the inrush current is greatly limited by be time it takes the heater of such a tube to come up to temperature. Granted, it comes up quickly in terms of vacuum tube heating time, and there is very little actual delay to the whole event, but compared to the virtually instant full conduction of SS rectifiers, the comparatively slow warm up time of a 5U4 heater still provides significant inrush protection.
That being said however, what an inrush device will do when a vacuum tube rectifier is used, is to limit the current drawn by the cold heaters at start up, which can be significant. In this way, an inrush limiter will be kinder to all of the heaters in the amplifier. But in terms of limiting significant B+ surge current of tradition designs employing vacuum tube rectifiers, their use is really inconsequential.
On a final note, they can also help with high line voltage conditions, as there is a drop across them even when fully warmed. Therefore, their use is helpful in those conditions. It won't hurt to install one when a vacuum tube rectifier is used, but in those conditions, the benefit is primarily to provide a gentle ramp up of heater current, rather than control surge B+ currents, as the tube has largely already done that.
Dave
That being said however, what an inrush device will do when a vacuum tube rectifier is used, is to limit the current drawn by the cold heaters at start up, which can be significant. In this way, an inrush limiter will be kinder to all of the heaters in the amplifier. But in terms of limiting significant B+ surge current of tradition designs employing vacuum tube rectifiers, their use is really inconsequential.
On a final note, they can also help with high line voltage conditions, as there is a drop across them even when fully warmed. Therefore, their use is helpful in those conditions. It won't hurt to install one when a vacuum tube rectifier is used, but in those conditions, the benefit is primarily to provide a gentle ramp up of heater current, rather than control surge B+ currents, as the tube has largely already done that.
Dave
marloubow
Best Day Ever
Guys,
Forgive me for slow responses...I'm a bit under the weather.
Rick, thanks for the nod! :thmbsp:
Bruce, thanks for chiming in. Your help on my 800c was much appreciated. I'm sure it will be no different here. Feel free to mark up the assembly instructions at any time. I do well with circles and arrows.
My fuse holder is smaller, which gives me even a bit more space for the CL-90(s).
Since I had to order all new components, I didn't order anything special to replace the "death cap". What I ordered was a 0.033uf /600V Vishay Poly orange. Is this adequate?
Dave...thanks for the input. Do you teach this stuff for a living? You have a way of expounding that is both clear and concise. :thmbsp:
So...I'm still unclear (may be the medication). I have a CL-90 for each unit at present. I can use both on the first unit and order two more (along with some safety caps) if need be (pita). But I'm not sure what is overkill and what is necessary here. Sorry for being dense.
thanks
martin
Forgive me for slow responses...I'm a bit under the weather.
Rick, thanks for the nod! :thmbsp:
Bruce, thanks for chiming in. Your help on my 800c was much appreciated. I'm sure it will be no different here. Feel free to mark up the assembly instructions at any time. I do well with circles and arrows.
My fuse holder is smaller, which gives me even a bit more space for the CL-90(s). Since I had to order all new components, I didn't order anything special to replace the "death cap". What I ordered was a 0.033uf /600V Vishay Poly orange. Is this adequate?
Dave...thanks for the input. Do you teach this stuff for a living? You have a way of expounding that is both clear and concise. :thmbsp:
So...I'm still unclear (may be the medication). I have a CL-90 for each unit at present. I can use both on the first unit and order two more (along with some safety caps) if need be (pita). But I'm not sure what is overkill and what is necessary here. Sorry for being dense.
thanks
martin
Martin -- From the standpoint of eliminating any and all surge currents, you only need one CL-90 for each amplifier. Placed it in series with one of the power transformer primary leads, and preferably the one connected to the hot side of the power source. You can use more than one device (in series), but that would only serve to reduce the ultimate operating voltages within the amplifier even further -- remembering that all of these devices have some voltage drop across them even when fully warmed.
It is just as much of a concern to have the operating voltages too low, as it is too high. Component life and performance can suffer if it deviates too far either way. One way to check if it is within acceptable limits is to measure the voltage produced at the 6.3 volt heater winding of the power transformer, when the amplifier is fully warmed and operating. Tube manufacturers allow as much as a 10% tolerance in heater voltage for traditional receiving tubes, but for best life and performance, this should be within +/- 5%. If it becomes too high, it can cause cathode material to evaporate at an excessive rate. To low, and it can poison the cathode from trying to draw current from it that it has not been sufficiently heated to deliver. If the voltage is outside this range, you can add an additional CL-90 (in addition to the initial one) if the voltage is high, or eliminate the CL-90s altogether if it is low.
Thanks for the kind words on my presentation. I do not teach professionally, but certainly remember what it was like when I had more questions than answers years ago. There are so many newcomers or folks returning to vacuum tube audio now days, but for me, it is a design format that I have never strayed from. So, I try to help when appropriate, and answer in a manner I would have wished for had the Internet been available to me when I had some of the same questions being asked today.
I have no doubt that your amplifiers will sound just as good as they look!
Dave
It is just as much of a concern to have the operating voltages too low, as it is too high. Component life and performance can suffer if it deviates too far either way. One way to check if it is within acceptable limits is to measure the voltage produced at the 6.3 volt heater winding of the power transformer, when the amplifier is fully warmed and operating. Tube manufacturers allow as much as a 10% tolerance in heater voltage for traditional receiving tubes, but for best life and performance, this should be within +/- 5%. If it becomes too high, it can cause cathode material to evaporate at an excessive rate. To low, and it can poison the cathode from trying to draw current from it that it has not been sufficiently heated to deliver. If the voltage is outside this range, you can add an additional CL-90 (in addition to the initial one) if the voltage is high, or eliminate the CL-90s altogether if it is low.
Thanks for the kind words on my presentation. I do not teach professionally, but certainly remember what it was like when I had more questions than answers years ago. There are so many newcomers or folks returning to vacuum tube audio now days, but for me, it is a design format that I have never strayed from. So, I try to help when appropriate, and answer in a manner I would have wished for had the Internet been available to me when I had some of the same questions being asked today.
I have no doubt that your amplifiers will sound just as good as they look!
Dave
marloubow
Best Day Ever
Gentlemen,
Tonight I got thru 1 of the 3 pages which make up the wiring and component assembly. If you haven't had a chance to work from one of these assembly manuals, it's really quite nice (says the noob) . They really put quite a bit of thought into the assembly process. With each connection, you're instructed not only on the termination point, but if you're to solder or just to connect for the time being. If you are instructed to solder a termination, it tells you how many other wires or component leads should be there to solder at the same time, thus ending your work for that terminal. They really had the novice in mind when they marketed these kits.
Dave, I'm going with you're recommendation on the CL-90's for now on two counts. One, It saves me from ordering 2 more + S&H and because of what you mentioned about fluctuating voltages. Last summer (our hottest on record), when trying to bias my Fisher 800c, I would get swings in our household current from 111V to 121V without a moments notice. I had to really work fast before some neighbor's A/C unit switched on and threw my measurements all to hell.
It may be a slow go here till after Christmas. I shouldn't hole up in the basement with family in town. :nono:
Thanks
martin
Tonight I got thru 1 of the 3 pages which make up the wiring and component assembly. If you haven't had a chance to work from one of these assembly manuals, it's really quite nice (says the noob) . They really put quite a bit of thought into the assembly process. With each connection, you're instructed not only on the termination point, but if you're to solder or just to connect for the time being. If you are instructed to solder a termination, it tells you how many other wires or component leads should be there to solder at the same time, thus ending your work for that terminal. They really had the novice in mind when they marketed these kits.
Dave, I'm going with you're recommendation on the CL-90's for now on two counts. One, It saves me from ordering 2 more + S&H and because of what you mentioned about fluctuating voltages. Last summer (our hottest on record), when trying to bias my Fisher 800c, I would get swings in our household current from 111V to 121V without a moments notice. I had to really work fast before some neighbor's A/C unit switched on and threw my measurements all to hell.
It may be a slow go here till after Christmas. I shouldn't hole up in the basement with family in town. :nono:
Thanks
martin
marloubow
Best Day Ever
Okay,
I've completed the assembly of the first mono block. I feel it's too late for a through go-thru on my part...I'm feeling a bit sleepy and fatigued. But thought it a good idea to give you all a look-see. Perhaps you may notice something obviously not right...heading off disaster.
I still don't understand the "preamp power" sockets. I don't know if I need the plug's wired and inserted for the amps to function or not.
The assembly instructions give me some resistance points to measure before applying AC power. But I'm unsure if the mods will skew the measurements.
My head is no shape to think any more on this.
Thanks
Martin
I've completed the assembly of the first mono block. I feel it's too late for a through go-thru on my part...I'm feeling a bit sleepy and fatigued. But thought it a good idea to give you all a look-see. Perhaps you may notice something obviously not right...heading off disaster.
I still don't understand the "preamp power" sockets. I don't know if I need the plug's wired and inserted for the amps to function or not.
The assembly instructions give me some resistance points to measure before applying AC power. But I'm unsure if the mods will skew the measurements.
My head is no shape to think any more on this.
Thanks
Martin
Martin -- Your work looks very neat and well executed. While I am not a fan of "mid air" connections, I also realize the change to modern components disturbed the original wiring plan. The new connections will certainly serve just fine for the new life of the amplifier, but a couple of extra terminal strips would secure the look of the original wiring plan as much as possible with the new components used.
The biggest issue I (think I) see is the size of the resistors you have used for the plate and cathode connections of the 6SN7. These were originally 1 watt devices in the Eico amplifiers, and even at that rating, they were underrated. It is extremely common to see the original components showing the effects of significant overheating due to this fact.
For the best long term performance, these resistors should be 2 watt devices. I can't tell for sure from your pics, but they appear to possibly be only .5 watt devices, which will not last long. I would double check this to be sure.
No doubt you will absolutely love the sound these amplifiers produce. I can't wait to hear your reaction to them!
Dave
The biggest issue I (think I) see is the size of the resistors you have used for the plate and cathode connections of the 6SN7. These were originally 1 watt devices in the Eico amplifiers, and even at that rating, they were underrated. It is extremely common to see the original components showing the effects of significant overheating due to this fact.
For the best long term performance, these resistors should be 2 watt devices. I can't tell for sure from your pics, but they appear to possibly be only .5 watt devices, which will not last long. I would double check this to be sure.
No doubt you will absolutely love the sound these amplifiers produce. I can't wait to hear your reaction to them!
Dave
marloubow
Best Day Ever
Dave,
I agree with you on mid air connections. I guess it just about the only draw back to too much room.
The can cap replacements (C1 and C2) are strapped to the original can cap leads, with insulating rubber between. They are also attached to the side of the chassis with 2 layers of double sided adhesive rubber tape at their "feet".
I still may add some support at the inrush limiter if I can find the right terminal strip. I don't want to have to drill any new holes into the chassis.
The 6SN7 resistors R14 & 17 are listed in parts as 1/2 watt...so that's what I got. I suppose another supply list is in order. I need a few items from radio daze. They have some 2 watt metal oxides in the values needed.
What else do I need to order guys? I'm not firing this amp up unless it's all A'Ok.
thanks
martin
I agree with you on mid air connections. I guess it just about the only draw back to too much room.
The can cap replacements (C1 and C2) are strapped to the original can cap leads, with insulating rubber between. They are also attached to the side of the chassis with 2 layers of double sided adhesive rubber tape at their "feet".
I still may add some support at the inrush limiter if I can find the right terminal strip. I don't want to have to drill any new holes into the chassis.
The 6SN7 resistors R14 & 17 are listed in parts as 1/2 watt...so that's what I got. I suppose another supply list is in order. I need a few items from radio daze. They have some 2 watt metal oxides in the values needed.
What else do I need to order guys? I'm not firing this amp up unless it's all A'Ok.
thanks
martin
Dandy -- you are exactly correct -- along with the 18K (originally) 1W cathode resistor used for the 6SN7 stage as well. All three of these components should be rated at 2 watts for stable, long term performance.
Dave
Dave