Pete, thumbs up for nice work ! Your amp should be good for another 50 years, if not neglected. It is worth pointing out that the original transformer and all parts are quite robust. Nobody NEEDS to go with all new PS board or XFMR to have a reliable SB-200 linear unless those parts are fried. It's nice but unless there is real damage, new caps and tubes, will make the SB-200 work fine. YES ! Either the soft key board or an external buffer ( MFJ/Ameritron ARB 704) is a must for solid state rigs to key this amplifier. My SB-200 has it's original filter caps and diodes and works fine. I had the opportunity to go through 4 SB-200's a few years back. All left here unmodified. A few caps were replaced, and other repairs done. None required any great expense. So, my point is that for $ 300-350 dollars you should be able to have a reliable amp and expect to see 500-550 watts output . If your diode/capacitor board is really compromised, it may be cheaper/better to replace it.. but replacing individual bad caps / diodes is perfectly viable and acceptable . Dirt and loose connections ( and disuse) are the biggest enemies of any transmitter or amp. In the process of cleaning your amp.. you will discover many little problems waiting to happen.. and hopefully you will make a list. Heath Engineering was really quite good..and while a lot of people have published a lot of "stuff" saying otherwise, the fact remains that these late 60's amps are still going strong 45 years later, and with very little effort on our parts. Each amp has to be evaluated individually.. so my comments are generalities, that don't take into account real abuse, accident or the "golden screwdriver". 73
+Capt Larry - Hi OM, Well Capt Larry I did want to have a reliable amp and when I considered buying a new one that would cost about $1K and probably not last through the warranty period. OR I could take an existing amp and install new heavy duty parts that would make it bullet proof and the cost was the same. That Peter Dahl transformer is superb and quite honestly the amp WILL DO 800 watts out --I don't suggest trying that with the heathkit OEM transformer or their rectifier board. The board I bought from W8CQ is far more robust than the heatkit board. The HV wiring as supplied with the original kit was under voltage --good for only 600 VDC --so my friend Heathkit cut corners. In fact I have two outstanding offers to purchase the amp for what I have in the amp -- so it was a worthwhile investment. Thank you for your comments and input.73'sPete N6QW
Yes nice job Pete. Hey I just bought a sb 200 and it's not producing any power? However the electrolytic capacitor caps are destroyed. Do you think that could be the issue? I know without looking you can't tell?
Hi Eric,Stop! There is lethal high voltage in the SB-200 and you must proceed with caution and do not do any troubleshooting with the SB-200 connected to any power source. With the electronic caps being destroyed very likely could have other attendant problems. These include a shorted HV transformer, blown finals, already destroyed filter caps, blown rectifiers and blown dropping resistors. As I did with this project --all of these items were replaced plus a lot more. Check Harbach Electronics --W8CQ (Jeff) for replacement parts -- that total may come close to well over $1000. If you bought this on eBay --see if you can return it unless you want to spend the cash and do a complete rebuild. I started with the idea of a complete rebuild as that was cheaper than buying an MFJ amp. 73'sPete N6QW
Pete first of all thanks for a nice video! Secondly i wanted to ask how did you you connect PA bypass switch. I just got my SB-200 and all mods are done including Harbach Soft Key. I've been looking on google but couldn't find any solution.
Hi Rafal. Thanks for your post. When I was looking to buy the amp on eBay I spotted that the bypass switch was already installed (nicely done and looks original). Plus the amp had no tu-bes which made the price attractive. The switch is in series with the keying line and since I have the Harbach SoftKey -- the switch simply opens up the keying line to the soft key. there is no magic here --just breaks the circuit
great job!! I also have a SB200. My power supply HV caps went burned the PCB. I am getting the same replacement board. I found OEM relay and fan on eBay. Hope to have it going in the next few months. ben in box 10 years needing parts.
Hi Mike, Thank you so much for your comments. I would only hope that the SB-200 video might be helpful to those who are contemplating a similar upgrade. The SB-200 is in use in daily service and I am very pleased. The more modern components don't like to be stressed too much. The HV capacitor bank is like trying to feed a dead short at turn on. The step start eases the HV on to the filter bank. Will it work without it - Yes? Will the caps last a long time without the SS, probably No.
Hi mac p, Thanks for looking at the video and your comment. Firstly it is probably best you contact W8CQ, Jeff who owns harbach and ask him about why an ac relay for use on dc. But you might want to do a bit of research on your own before doing that. If you inquire on Google can you use an AC relay with DC -- you will find that you can although not directly. You have to use less (LESS) DC voltage on the AC relay. If you look at Harbach's listing on the replacement relay you will see you also get a different dropping resistor (LESS DC) that must be installed. The Heathkit SB-200 uses a unique system for cutting off the amp when you are receiving and when you have the amp in line. If you didn't cut the tubes off during receive you would hear "hash" in the receiver. To completely cut-off the tubes heath used a negative 120 volts DC which was fed into the grids of the 572B's through the coil of the relay. So the first problem was that somehow you must ground that -120 volts to do two things 1) is remove the bias from the tubes and 2) operate the TR sequence. If you study the schematic you will also se that there is a small amount of bias on the grids after the TR initiation and this is the normal operating bias for the 572B's Now at the time the SB200 was designed -- most of the transceivers were tubes and typically there was a relay inside the transmitter or transceiver that provided a contact closure so it was pretty easy to directly switch on and switch off the linear. With the advent of Solid State rigs --the amp keying was done with devices and not relays --so if you connected your very expensive SS rigs directly to the SB200 you would smoke it. Harbach solved that problem with the soft key accessory so you could key the amp with a SS rig. Now circling back. That SB200 has been around for a long time and many pieces of hardware common in 1970 are no longer manufactures. I do not know this fo a fact but likely the use of the AC relay is a workaround for the non availability of the original part. Again contact harbach and get a direct answer but most likely if you operate the AC relay and less voltage using DC --it works. It all has to do with the magnetizing force that is developed in the field coil and the applied voltage values for engagement are different depending on whether it is AC or DC. 73's Pete N6QW
Checked the wiring over and all looks good if I ground the center of the ant relay I should get the amp to switch but its not do I need a ant connected to the rf input or not just for testing also do you have an email address
How do you test the softkey I have installed it and on the center pin I get about 1.6volts AC nothing DC I just wondered if there was any way of testing the soft key before putting it all back together again
Hi Andrew, I don't have a good answer for you other than I carefully built the unit and it worked. Might I suggest you contact W8CQ who owns the Harbach company now and perhaps he can further answer your question. Did you check your wiring to assure it is correct? 73's Pete N6QW
Great mods , I'm just not sold on the soft start , to me it's kinda snake oil, I realize what it's trying to do but ... The amp has been running for 40-50 years fine with out it. The new power board and soft key I get and have ordered .
Hi Edgar T -- am not sure how you would do that as I am not familiar with the SB201. I think that model skipped 10 Meters. But I just don't know how you would do that.Pete N6QW
@@darrelldundee7198 The primary side input voltage is 220. Despite what manufacturers tell you --always best to run linear amps on 220. The higher voltage is less stressful on your house wiring and it actually gets full output as there is no sag on the primary side. It would not be uncommon to see a 12 amp draw on voice peaks on 110 --kind of hard on a 15 amp circuit as likely you have other stuff connected to the same outlets. On 220 that draw is only 6 amps! Hope that answers your question. Pete N6QW
Wonderful job! Just completed my SB200 refurb also using the Harbach power supply and soft key products. Works great!
Pete, thumbs up for nice work ! Your amp should be good for another 50 years, if not neglected. It is worth pointing out that the original transformer and all parts are quite robust. Nobody NEEDS to go with all new PS board or XFMR to have a reliable SB-200 linear unless those parts are fried. It's nice but unless there is real damage, new caps and tubes, will make the SB-200 work fine. YES ! Either the soft key board or an external buffer ( MFJ/Ameritron ARB 704) is a must for solid state rigs to key this amplifier. My SB-200 has it's original filter caps and diodes and works fine. I had the opportunity to go through 4 SB-200's a few years back. All left here unmodified. A few caps were replaced, and other repairs done. None required any great expense. So, my point is that for $ 300-350 dollars you should be able to have a reliable amp and expect to see 500-550 watts output . If your diode/capacitor board is really compromised, it may be cheaper/better to replace it.. but replacing individual bad caps / diodes is perfectly viable and acceptable . Dirt and loose connections ( and disuse) are the biggest enemies of any transmitter or amp. In the process of cleaning your amp.. you will discover many little problems waiting to happen.. and hopefully you will make a list. Heath Engineering was really quite good..and while a lot of people have published a lot of "stuff" saying otherwise, the fact remains that these late 60's amps are still going strong 45 years later, and with very little effort on our parts. Each amp has to be evaluated individually.. so my comments are generalities, that don't take into account real abuse, accident or the "golden screwdriver". 73
+Capt Larry - Hi OM, Well Capt Larry I did want to have a reliable amp and when I considered buying a new one that would cost about $1K and probably not last through the warranty period. OR I could take an existing amp and install new heavy duty parts that would make it bullet proof and the cost was the same. That Peter Dahl transformer is superb and quite honestly the amp WILL DO 800 watts out --I don't suggest trying that with the heathkit OEM transformer or their rectifier board. The board I bought from W8CQ is far more robust than the heatkit board. The HV wiring as supplied with the original kit was under voltage --good for only 600 VDC --so my friend Heathkit cut corners. In fact I have two outstanding offers to purchase the amp for what I have in the amp -- so it was a worthwhile investment. Thank you for your comments and input.73'sPete N6QW
Yes nice job Pete. Hey I just bought a sb 200 and it's not producing any power? However the electrolytic capacitor caps are destroyed. Do you think that could be the issue? I know without looking you can't tell?
Hi Eric,Stop! There is lethal high voltage in the SB-200 and you must proceed with caution and do not do any troubleshooting with the SB-200 connected to any power source. With the electronic caps being destroyed very likely could have other attendant problems. These include a shorted HV transformer, blown finals, already destroyed filter caps, blown rectifiers and blown dropping resistors. As I did with this project --all of these items were replaced plus a lot more. Check Harbach Electronics --W8CQ (Jeff) for replacement parts -- that total may come close to well over $1000. If you bought this on eBay --see if you can return it unless you want to spend the cash and do a complete rebuild. I started with the idea of a complete rebuild as that was cheaper than buying an MFJ amp. 73'sPete N6QW
Pete first of all thanks for a nice video! Secondly i wanted to ask how did you you connect PA bypass switch. I just got my SB-200 and all mods are done including Harbach Soft Key. I've been looking on google but couldn't find any solution.
Hi Rafal. Thanks for your post. When I was looking to buy the amp on eBay I spotted that the bypass switch was already installed (nicely done and looks original). Plus the amp had no tu-bes which made the price attractive. The switch is in series with the keying line and since I have the Harbach SoftKey -- the switch simply opens up the keying line to the soft key. there is no magic here --just breaks the circuit
Got it. Thanks for fast answer and once again - nice video! 73
great job!! I also have a SB200. My power supply HV caps went burned the PCB. I am getting the same replacement board. I found OEM relay and fan on eBay. Hope to have it going in the next few months. ben in box 10 years needing parts.
Hi Mike,
Thank you so much for your comments. I would only hope that the SB-200 video might be helpful to those who are contemplating a similar upgrade. The SB-200 is in use in daily service and I am very pleased. The more modern components don't like to be stressed too much. The HV capacitor bank is like trying to feed a dead short at turn on. The step start eases the HV on to the filter bank. Will it work without it - Yes? Will the caps last a long time without the SS, probably No.
Question: Why does Harbach sell you an AC relay when the voltage is DC?
Hi mac p,
Thanks for looking at the video and your comment.
Firstly it is probably best you contact W8CQ, Jeff who owns harbach and ask him about why an ac relay for use on dc.
But you might want to do a bit of research on your own before doing that. If you inquire on Google can you use an AC relay with DC -- you will find that you can although not directly. You have to use less (LESS) DC voltage on the AC relay. If you look at Harbach's listing on the replacement relay you will see you also get a different dropping resistor (LESS DC) that must be installed.
The Heathkit SB-200 uses a unique system for cutting off the amp when you are receiving and when you have the amp in line. If you didn't cut the tubes off during receive you would hear "hash" in the receiver. To completely cut-off the tubes heath used a negative 120 volts DC which was fed into the grids of the 572B's through the coil of the relay. So the first problem was that somehow you must ground that -120 volts to do two things 1) is remove the bias from the tubes and 2) operate the TR sequence. If you study the schematic you will also se that there is a small amount of bias on the grids after the TR initiation and this is the normal operating bias for the 572B's
Now at the time the SB200 was designed -- most of the transceivers were tubes and typically there was a relay inside the transmitter or transceiver that provided a contact closure so it was pretty easy to directly switch on and switch off the linear. With the advent of Solid State rigs --the amp keying was done with devices and not relays --so if you connected your very expensive SS rigs directly to the SB200 you would smoke it. Harbach solved that problem with the soft key accessory so you could key the amp with a SS rig.
Now circling back. That SB200 has been around for a long time and many pieces of hardware common in 1970 are no longer manufactures. I do not know this fo a fact but likely the use of the AC relay is a workaround for the non availability of the original part.
Again contact harbach and get a direct answer but most likely if you operate the AC relay and less voltage using DC --it works. It all has to do with the magnetizing force that is developed in the field coil and the applied voltage values for engagement are different depending on whether it is AC or DC.
73's
Pete N6QW
Checked the wiring over and all looks good
if I ground the center of the ant relay I should get the amp to switch but its not do I need a ant connected to the rf input or not just for testing also do you have an email address
I picked up one yesterday with a blow power bord
How do you test the softkey I have installed it and on the center pin I get about 1.6volts AC nothing DC I just wondered if there was any way of testing the soft key before putting it all back together again
Hi Andrew,
I don't have a good answer for you other than I carefully built the unit and it worked. Might I suggest you contact W8CQ who owns the Harbach company now and perhaps he can further answer your question. Did you check your wiring to assure it is correct?
73's
Pete N6QW
Great mods , I'm just not sold on the soft start , to me it's kinda snake oil, I realize what it's trying to do but ... The amp has been running for 40-50 years fine with out it. The new power board and soft key I get and have ordered .
got it working if I put the blue wire to ground the relay now switching needs new connection on the back panel
is it wired for 220 volt kj3a
Thanks for your comment. The amp is really perking along nicely --so I am very happy that I chose this alternative.
73's
Pete N6QW
GREAT job! Impressive :)
I have a Heathkit sb 201 how can I mod it for 11 meter
Hi Edgar T -- am not sure how you would do that as I am not familiar with the SB201. I think that model skipped 10 Meters. But I just don't know how you would do that.Pete N6QW
OK thanks for getting back to me
You don't you get a ham license and expand your hobby 👌
good work presentation needs some work hard to follow.
HI Stanley,Thanks for your input. Pete N6QW
@@N6QW is it wired for 220 volt tnx de kj3a
@@darrelldundee7198 The primary side input voltage is 220. Despite what manufacturers tell you --always best to run linear amps on 220. The higher voltage is less stressful on your house wiring and it actually gets full output as there is no sag on the primary side. It would not be uncommon to see a 12 amp draw on voice peaks on 110 --kind of hard on a 15 amp circuit as likely you have other stuff connected to the same outlets. On 220 that draw is only 6 amps!
Hope that answers your question.
Pete N6QW
@@N6QW ok tnx sir problems solved
thanks super job oz1cfo
ps THANK YOU