Heathkit Sb 303 Manual

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Heathkit Sb 303 Manual

Heathkit Sb 303 Manual User
Heathkit Sb 303 Manual Online
I had originally intended to publish a more extensive article, but havemoved on to other projects. I am sharing here some tips that you mayfind useful. I always coveted the Heathkit Twins, but could neverafford them. A friend was cleaning out his basement and passed thesealong at a reasonable price. I now had the opportunity to enjoy adream from the past.

These are the early filter type sideband rigs from the sixties, so be awareof their limitations. The spurious output performance is better thanthe Heathkit Marauder, the previous SSB rig. Unless the trap wasadjusted carefully, the spur on 20 meters was a problem. Drift wasgreatly improved by the new LMO in the twins. The Marauder occupieda monster Apache cabinet and was similar in appearance to the Apache. The SB401 and SB301 are significant improvements over the earlyversions. In particular, the transmitter is much easier to switchfrom split to transceive. A small reed relay to switch the VFOaround would correct this in the early 400. The 300 is an excellentreceiver, especially if it has the accessory AM and CW filters. The301 was friendlier to the 6 and 2 meter converters, but no othersignificant changes.
The SB303 was an all solid state receiver, the last in the series. Iplan to do a write up on this project later, as this is part of mypermanent collection.
Compactron tubes are used extensively in the transmitter. These are gettingscarce. Stock up on them while you still can. The receiver has onlyone compactron. It can be replaced with a 12AU7 and 6AU6, if you areclever.
The transmitter was improved by inserting 10 Ohm resistors at various B+points. It did give the kit builder a 'second chance' ifthere were shorts. The resistors smoked to alert the owner oferrors. Perhaps you could recover from them if you killed the powerquickly. More significantly, the 82K resistor on the terminal boardunderneath in the front was changed to 2 Watt. You should check thisbefore power up. As a minimum, the CW & Tune Drive adjust willnot work right if the value goes up. If it goes down in value, thebalanced modulator diodes will fail and other ugly things will occur.
The antenna relay (not the main control relay) also develops a permanentmagnetism that causes it to hang up in transmit mode. I have seenpeople put thin pieces of plastic on the pole piece to fight this. The easiest way to correct this is to use a powerful tape headdemagnetizer to reduce the residual magnetism. Then swap the wiresto the coil of the relay; it will probably magnetize again, but itwill take quite a while. If it happens again, just swap them back.
Overall view and on-the-air demo of this ssb transmitter. Download HEATHKIT SB-303 SOLID-STATE SSB RECEIVER SERVICE MANUAL service manual & repair info for electronics experts. Service manuals, schematics, eproms for electrical technicians. This site helps you to save the Earth from electronic waste! HEATHKIT SB-303 SOLID-STATE SSB RECEIVER SERVICE MANUAL.
Follow the manual during alignment. Be sure to perform the neutralizationcarefully. Power output will be 100 Watts, but lower on 15 and 10meters for sure. If you get 75 Watts on 10 Meters, call it good. Use the grid drive meter to determine if the power is not up tosnuff. If you are not getting enough grid drive, changing the finalswill not correct it. Low B+ on the low voltage or resistors thathave drifted in value can cause the exciter to not deliver enoughdrive to the finals to operate properly.
Operating the Heath Twins as a complete station requires the constructionof three cables each exactly 24' long from RG-62/U coaxial cable (90 Ohms)exactly as described in the SB300/301/303 receiver manual. Yes, thetransmitter connection is described in the receiver manual. The cable partscame with the receiver, not the transmitter. Go figure. Anyway, theimpedance is not relevant. The shunt capacitance per foot is very critical,since it can detune the circuits which are used to link the receiver to thetransmitter. The crystal HF oscillator in the receiver is used to drive thetransmitter. The USB and LSB BFO crystals in the receiver are used tooperate the transmitter. In the SB400, you may find it advantageous toremove the BFO crystals EXCEPT THE CW crystal, to prevent a beat note onreceive. The CW crystal is required to operate CW and Tune modes. I do notknow if the 401 requires this, but try it if you have problems. The LMO(VFO) is linked between the two rigs for transceive, and is the ONLYoscillator switched to go to split frequency operation. In a pinch, I haveheard that some people will disassemble a junked AM car radio antenna,which often uses a similar coax cable. I have a quantity of the correctcoax on hand, which I have often mailed to those who need this item.
The LMO sometimes develops a jump or warble as you tune in a station that is annoying in CW or SSB modes. This is a link to fix that problem: http://nebula.wsimg.com/d6a8106142d2492dec285d95be47aaf6?AccessKeyId=D1250C433DB440D6B60D
NOTE: The SB400/401 often comes WITHOUT the crystal pack. You do not needANY crystals (except the CW crystal) installed to operate the transmitter,if you are using it with a Heath SB300/301/303. For troubleshootingpurposes, to operate the SB400/401 as a stand alone unit, simply 'borrow'one or more crystals from the SB300 until you can get the SB400 running.Then connect them as described above. Note also that you have to re-alignthe HF oscillator coils as described in the manual as well as some otheradjustments. Since the crystals for 29.0 to 29.5 and 29.5 to 30 MHz coveredterritory for AM and FM, many did not install the crystals in a SSB/CW onlyrig. Again, the receiver came with the whole set; use the cables describedabove and you have no problem.
UPDATE -I have heard one report for VFO changing frequency when switching to transmit. I have never encountered this myself. I found the voltage regulation built in OK. The person told me he added another VR tube. I am not sure that the power supply capacitors, resistor values drifted, or something else may have been off. But this is added as a cautionary note, in case you have problems.

These are the early filter type sideband rigs from the sixties, so be awareof their limitations. The spurious output performance is better thanthe Heathkit Marauder, the previous SSB rig. Unless the trap wasadjusted carefully, the spur on 20 meters was a problem. Drift wasgreatly improved by the new LMO in the twins. The Marauder occupieda monster Apache cabinet and was similar in appearance to the Apache. The SB401 and SB301 are significant improvements over the earlyversions. In particular, the transmitter is much easier to switchfrom split to transceive. A small reed relay to switch the VFOaround would correct this in the early 400. The 300 is an excellentreceiver, especially if it has the accessory AM and CW filters. The301 was friendlier to the 6 and 2 meter converters, but no othersignificant changes.
The SB303 was an all solid state receiver, the last in the series. Iplan to do a write up on this project later, as this is part of mypermanent collection.
Compactron tubes are used extensively in the transmitter. These are gettingscarce. Stock up on them while you still can. The receiver has onlyone compactron. It can be replaced with a 12AU7 and 6AU6, if you areclever.
The transmitter was improved by inserting 10 Ohm resistors at various B+points. It did give the kit builder a 'second chance' ifthere were shorts. The resistors smoked to alert the owner oferrors. Perhaps you could recover from them if you killed the powerquickly. More significantly, the 82K resistor on the terminal boardunderneath in the front was changed to 2 Watt. You should check thisbefore power up. As a minimum, the CW & Tune Drive adjust willnot work right if the value goes up. If it goes down in value, thebalanced modulator diodes will fail and other ugly things will occur.
The antenna relay (not the main control relay) also develops a permanentmagnetism that causes it to hang up in transmit mode. I have seenpeople put thin pieces of plastic on the pole piece to fight this. The easiest way to correct this is to use a powerful tape headdemagnetizer to reduce the residual magnetism. Then swap the wiresto the coil of the relay; it will probably magnetize again, but itwill take quite a while. If it happens again, just swap them back.
Overall view and on-the-air demo of this ssb transmitter. Download HEATHKIT SB-303 SOLID-STATE SSB RECEIVER SERVICE MANUAL service manual & repair info for electronics experts. Service manuals, schematics, eproms for electrical technicians. This site helps you to save the Earth from electronic waste! HEATHKIT SB-303 SOLID-STATE SSB RECEIVER SERVICE MANUAL.
Follow the manual during alignment. Be sure to perform the neutralizationcarefully. Power output will be 100 Watts, but lower on 15 and 10meters for sure. If you get 75 Watts on 10 Meters, call it good. Use the grid drive meter to determine if the power is not up tosnuff. If you are not getting enough grid drive, changing the finalswill not correct it. Low B+ on the low voltage or resistors thathave drifted in value can cause the exciter to not deliver enoughdrive to the finals to operate properly.
Operating the Heath Twins as a complete station requires the constructionof three cables each exactly 24' long from RG-62/U coaxial cable (90 Ohms)exactly as described in the SB300/301/303 receiver manual. Yes, thetransmitter connection is described in the receiver manual. The cable partscame with the receiver, not the transmitter. Go figure. Anyway, theimpedance is not relevant. The shunt capacitance per foot is very critical,since it can detune the circuits which are used to link the receiver to thetransmitter. The crystal HF oscillator in the receiver is used to drive thetransmitter. The USB and LSB BFO crystals in the receiver are used tooperate the transmitter. In the SB400, you may find it advantageous toremove the BFO crystals EXCEPT THE CW crystal, to prevent a beat note onreceive. The CW crystal is required to operate CW and Tune modes. I do notknow if the 401 requires this, but try it if you have problems. The LMO(VFO) is linked between the two rigs for transceive, and is the ONLYoscillator switched to go to split frequency operation. In a pinch, I haveheard that some people will disassemble a junked AM car radio antenna,which often uses a similar coax cable. I have a quantity of the correctcoax on hand, which I have often mailed to those who need this item.
The LMO sometimes develops a jump or warble as you tune in a station that is annoying in CW or SSB modes. This is a link to fix that problem: http://nebula.wsimg.com/d6a8106142d2492dec285d95be47aaf6?AccessKeyId=D1250C433DB440D6B60D
NOTE: The SB400/401 often comes WITHOUT the crystal pack. You do not needANY crystals (except the CW crystal) installed to operate the transmitter,if you are using it with a Heath SB300/301/303. For troubleshootingpurposes, to operate the SB400/401 as a stand alone unit, simply 'borrow'one or more crystals from the SB300 until you can get the SB400 running.Then connect them as described above. Note also that you have to re-alignthe HF oscillator coils as described in the manual as well as some otheradjustments. Since the crystals for 29.0 to 29.5 and 29.5 to 30 MHz coveredterritory for AM and FM, many did not install the crystals in a SSB/CW onlyrig. Again, the receiver came with the whole set; use the cables describedabove and you have no problem.
UPDATE -I have heard one report for VFO changing frequency when switching to transmit. I have never encountered this myself. I found the voltage regulation built in OK. The person told me he added another VR tube. I am not sure that the power supply capacitors, resistor values drifted, or something else may have been off. But this is added as a cautionary note, in case you have problems.
Complete Transceivc capabilities are available when the Transmitter is used with the Healhkit Model SB-300, SB-SOl, or 83-303 Receiver. The Transmitter can also be used with other receivers by installing the SBA-4014 Crystal Accessory Kit in the Transmitter. This Transmitter is compatible with the Heathkit Model SB-200 SSB Linear Amplifier. SB-303 Amateur-R Heathkit Brand, Heath Co.; Benton Harbor MI, build 1970–1976, 13 pictures, 4 schematics, 27 semiconductors, United States of America.
Good luck with your restoration. These have nice audio on transmit. TheALC circuitry works better than the transceiver SB100.
GUEST UPDATE 4/19/2014 -I was studying the schematic for the SB-300 and found an error on theheterodyne crystal oscillator switch wafer labeled BS1R. The commonconnection for crystals Y6, Y5,Y2 and lastly Y1 should be grounded. Rightnow without any connection, one side of all of these crystals are floating.They do have it correct for Y3, Y4,Y7 and lastly Y8. This is just aschematic drawing mistake and obviously the wiring of the receiver iscorrect since the receiver works!
 73,
 Joe, W3GMS
UPDATE 7/12/2016 -One more Heathkit Twins glitch is addressed at:http://www.boatanchor.com/heath/SB300-SB301%20Voltage%20Regulation%20.pdf.I have not personally tried this modification myself, but it appears to be carefully researched and implemented. Please keep in mind that the SSB equipment of this day was not very stable; people were using SB-10 adapters driven by DX-100 VFOs that were barely stable enough for AM, marginal for CW, and totally unacceptable for SSB. Comparing first or second generation SSB gear to modern rigs is just not reasonable.
Heathkit Sb 303 Manual UserSB-303 Assembly manual.zip: 19.800 Kbytes: SB-310 Service manual.zip: 3.631 Kbytes: SB-401 Manual.zip: 9.055 Kbytes: SB-500 2-Meter Transverter Schematic.zip. This is all the manuals for Heathkit. If you want to see manuals from other manufactories you can click on the manufactory menu in.
Heathkit Sb 303 Manual OnlineN4UERating: 2017-07-29
Liked it so much I bought anotherTime Owned: 3 to 6 months.
I collect receivers. Have a LOT, but I was so impressed with the initial SB-303, I bought another.
 It came up on eBay for a very low 'buy it now' price. Had the usual 'parts/not working' caveat.
 It arrived with the best packing I've seen in many years.
 Out of the box it was dead, but as expected of this vintage radio, all it tool was some careful application of DeOxit. The face of the radio looks like the day it was built.
 I haven't even gone through the alignment yet, but it works excellent.
 If you work on enough of these SB-3XX series, you can get pretty good getting the tuning mechanism working 'ok'....
 Not like my Collins radios, but close.
 Have fun.
 ron
 N4UE
----------------------
Earlier 5-star review posted by N4UE on 2017-07-06
I've recently been on a Heathkit receiver spree. I purchased a 301, a 300, and just a couple of days ago, I got a 303.
 I was kinda wary because of the radio's mixed reviews. Like the 301 and 300, this radio had all three filters, which is a nice touch. This example was well built and the tuning mechanism works perfectly. I had to adjust one of the other receivers, but having been through this (in great pain) with my 75S-3, it was not difficult.
 Too sensitive? Yes, it has great sensitivity but I cannot understand why ops don't understand RF Gain and ATTENUATOR. 
 This example has one issue. The S-Meter is intermittent. A new one is one the way.
 BTW, a 'gotcha' that got me. I replace the dial lamps in all my radios with LEDs. I buy them by the 100.
 The dial lamps in the 303 are 3 #47s in SERIES.
 Back to the bulbs until I come up with a solution......
 Great radio and enjoy the hobby.
 ron
 N4UE
KI6EQWRating: 2010-01-03
I was surprised!Time Owned: 3 to 6 months.
Purchased on Ebay for a little over $200. Unit was in nice condition with all three filters. Usual cracks on the dial, but minor in nature. Plugged it in, and no signal/volume. Contacted the seller who said it worked when in his possession, but he agreed to split repair costs--an honest seller. Contacted RTO, and away it went for 45 days. Repairs were $95 bucks. LMO needed lubrication, set needed alignment, everything else was OK. Unit came back, and same problems. The description of work by RTO gave me a clue as to the problem, and the tape along the bottom of the RF, and audio boards confirmed it, the two boards had simply wiggled loose during shipping. I reseated them, and voila,the radio was perfect. I was very pleased with its performance, and the addition of a Timewave DSP 9+, made it all the better. Ebay is a mixed bag, and I usually assume there will be something wrong with the piece when it arrives . I stay away from sellers without call signs unless it is a low cost item. Enjoy the SB-303, it is a very nice unit for its time, and fun to use. 
WA4AOSRating: 2010-01-03
Almost DecentTime Owned: more than 12 months.
As the last reviewer said, it's basically a nice radio but like all of the SB series, the dial mechanism stinks and that's putting it mildly. Many of the examples I have worked on in recent years often have a crack in the dial if not several and are usually have a crazed background.
 In my business, I service mainly R 390, R 390A, R 392 receivers as well as some Drake C lines and Hammarlund HQ 1XX receivers. 
 I often work on SB gear as well and have been considering for some time redesigning and making available replacement dials for the SB series. 
 I would probably only make the dial KHz and MHz parts available and would strive to have the same visual effect but a more reliable tuning mech.
 There are many SB XXX's still in use and with the interest in vintage gear these days, it might be worth my time and investment to make a kit available. I would be lucky to break even on a project like this but who knows.
 I would welcome any comments or feedback with regard to interest in an improved tuning mech.
 I consider the SB 300, 301 and 303 to be fairly decent receivers, especially if one becomes aware of the need to reduce the RF gain and not keep it at full throttle all of the time. The sensitivity on all of these receivers is well below a microvolt and in the case of the 301 and 303 below half a microvolt. The audio quality is decent and selectivity fine for non contest type operation. With the CW filter available for the 301 and 303, great CW selectivity is available but with no notch or variable bandwidth adjustment, I would not find either of these to be the best choice for serious contesting in today's high performance receiver markets.
 Of course in the 70's an SB 301 0r 303 was considered almost top shelf behind a Drake B or C line or possibly a Collins S line.
 There is at least one company that sells a digital display that can be installed in place of the MHz indicator of these units but that really detracts from the vintage look. 
 Anyway, it would be interesting to see if there is interest in a replacement tuning dial. I would probably go with a simular design but use a CNC brass spiral for the ceter and a dial more like the one used in the HW 101.
 In my humble opinion, I actually prefer the dial used in the HW 101. True, it's 5 KHz resolution is not as good as 1Khz but at least it is more consistent in performance and gives very little trouble.
 73,
 Glenn 
 DSM Labs
WA7VTDRating: 2009-09-28
Bad Dial Design Eclipses Fine ReceiverTime Owned: 6 to 12 months.
PREFATORY NOTE: That negativity which I do have about this receiver is the same I harbor for all Heathkits of that vintage: the main dial tuning mechanism SUCKS! Getting it working properly again is quite a pain. I truly loathe that SB tuning mechanism. Why Heathkit kept right on going with that design rather than something new, different and reliable after a few years of undoubtedly receiving a steady stream of complaints, is beyond me.
 RECENT OBSERVATIONS: 
 I have been burned three out of four times procuring SB-303s on e-Bay. The most recent acquisition was described by a prolific e-Bay seller (the one usually claiming to be THE Resident Collins man) as being 'Collector quality!' It arrived with scuffed cabinet, paint flaking off, and 100% slippage of the tuning mechanism.
 I managed to cannibalize one along with taking parts from a partial unit (I had bought a 303 chassis without the cabinet but with all the boards for $5 in another auction) and assemble a very cosmetically nice piece with what should have been very good electrical properties. 
 Unfortunately, the AM filter I pulled from another unit, was defective. The rig worked very well otherwise for about a month, and then died. Thus far I haven't been successful isolating the trouble but haven't put my mind to it yet, having burned myself out on the Heathkit station project after all of the mechanical work on the rig this morning, all because of that &^%$!! tuning dial mechanism!
 NEGATIVES:
 As with the tuning mechanism, the 303 suffers from the same problem as other SB-series rigs, with regard to the frequency calibration correction indicator. In time, the relatively soft plastic of the movable clear plastic panel inscribed with the vertical calibration correction line simply gets worn down ever so slightly along its edge and ceases to make good and regular contact with the correction control.
 POSITIVES:
 When working as per specs and with the *&^%$ tuning dial mechanism working smoothly, the 303 is a really fun ham band receiver that works great with the SB-400 or 401 for separate/slaved operation. Personally, I prefer running them separate (i.e., non-slave but otherwise interconnected for transceive) in order to use the SB-650 digital frequency readout on the 303. You can't use the SB-650 and run the two radios in slave, you must choose one configuration or the other. Also, the 303 as wired per standard instructions, won't support the SB-650 (it will produce a readout, just not one accurate to within several MHz and oddball kHz). Note: you must do a very simple mod on the 303 in order for it to support the SB-650. Plenty of extra RCA jacks are thoughtfully provided on the rear of the 303's chassis for that purpose, and the easy mod (involving generally the mere soldering of some capacitors) is well-described and illustrated in the SB-500 construction manual. 
 It's a hot receiver! The blocking dynamic range leaves something to be desired but what do you expect given the vintage? It's actually pretty good for its vintage. Set it next to a 75S-1 and you'll see why the Heathkits of this era were known to some as the 'poor man's Collins S-line).The SSB audio is crisp. If it had a notch filter it would really rock. The 1-kHz frequency resolution is, in my experience typically accurate to within 1.5 kHz across the entirety of a particular ham band after a single calibration on that band's lower edge using the 100 kHz/25 kHz crystal calibrator.
 The provision of 15 MHz for WWV reception -- useful in calibration, etc. -- is great. 
 Another thing on the plus side of the ledger: the 303 is super-light. You can tuck it under an arm and take it anywhere that its size isn't a problem. 
 As of this morning, I now have no working SB-303s. I spent hours getting the main tuning mechanism working well on two of them, and the one with a perfect tuning mechanism stopped working after re-attachment of the cover.
 I concur about the extender boards; if you see them, buy them. Otherwise, troubleshooting the various boards is quite difficult.
 On the other hand, the various boards -- removed from other 303s -- are not infrequently available cheap. It's pretty easy to isolate most problems to a particular board and then to replace the entire defective board in literally less than a minute.
 Also, this is one kit in which the assembler had few opportunities to screw it up. There is little point-to-point wiring. 
 I would give the 303 a 3 or 4 (taking into account its price class and design in its era of production) but I simply can't do that in view of the unremedied tuning mechanism problems.
 So, it's with mixed feelings and regret that I ultimately urge a '2' on this rig solely due to the ubiquitous and notorious dial tuning mechanism
 problem (which you might not encounter, though odds are you eventually will)that should have been remedied by Heath. Otherwise, I'd venture a 3 or 4 (it's no SX-115, so not a 5). 
 If you get your hands on a good one, keep it! 
VO1MDSRating: 2006-11-19
Simply the best !!Time Owned: 0 to 3 months.
 Well folks,what can i say that wasnt said already??
 well for one,this is a great old radio,lots of sensitivity,rock solid frequency stibility,for an analog receiver,this it the most stable analog radio that i have owned to date! now thats saying something,i have owned many,and i mean MANY analog recievers,and nothing that i have owned yet even compeats to the heathkit sb-303. what a great radio,what a great design,what a company.
 WAY TO GO HEATHKIT...A JOB WELL DONE.
 considering i bought the sb-303 AND the sb-401 for $50.00 i think i got a pretty wild bargin.
 all the best folks,have super fun with your sb-303,the best stable analog radio on da go.
 PERIOD!!
KG6UEQRating: 2005-06-11
Beware of this oneTime Owned: 0 to 3 months.
This radio's tuning assembly is prone to slippage. A small drive wheel, if not properly aligned, will slip off the larger wheel connected to the tuning mechanism. If you can be sure the radio you're buying does NOT have this problem, then you may be able to enjoy this vintage set.
W1FPRating: 2005-03-01
advanced for its ageTime Owned: more than 12 months.
My wife bought me this rx on our first xmas together. What better gift could you hope for. After 35 years, it still works fine. Yes, the dynamic range is quite poor, and in line with the devices available at the time. But stability of the LMO is excellent, and sensitivity is great. Yes, there is filter blow-by, but matched up with an SB-400 or SB-401, makes for an attractive vintage solid state pair.
N7EKXRating: 2005-02-11
Best Heathkit Receiver Out ThereTime Owned: 0 to 3 months.
 As a Heathkit fanatic, despite repeated warnings from friends, I bought an SB-303 from an eBay auction recently (for $172.00, plus shipping). The specs on its sensitivity were the reason I was ready to 'take the plunge' (and the risk it would arrive DOA). Anyway, the seller was totally honest, and I couldn't be happier. Both the receiver sensitivity and the 'LMO' stability are far better than the SB-104A that I built, and everything about the radio is high quality. Most old radios drift pretty badly after startup, but not this one... it's rock steady. No tubes, just transistors, FET's and other solid-state circuitry that works as well today as in 1976. There is no backlash in the dial, either. Maybe I just got lucky, but this SB-303 is as sensitive and stable as any analog radio out there, in my opinion!
ON4QJRating: 2004-12-25
Golden classicTime Owned: more than 12 months.
I bought 6 years back an SB-303 receiver,
 It looked ok on the outside,When i opened it
 it was like a 'warzone',Someone has done a great 
 job in messing up this radio.
 After some months of 'patching up' i had a great receiver,On 40 and 80 the RX is better than with my TS 570DG.
 Later i found an SB 401 Transmitter to connect it.
 And the SB 610 Station monitor.
 It is realy a great Rig to use and is for shure my number one radio!!
 Only shame is that we don't find much Heath stuff
 in Europe,...
 ON4QJ,Erwin
NO9ERating: 2004-05-08
Pretty good after minor modsTime Owned: more than 12 months.
I got one used. Bad intermod on 40m and poor sensititivity on 15-10m but very good AGC and not bad SSB and CW filters. Needed alignment, attenuator for 40m, and post-crystal_filter amplifier for sensitivity. After that, I liked it very much. Sensitivity as good as any on all bands, and a real DX digger on 80m.
 Ignacy, NO9E 
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