I refined further my list of mods. Looking deeper into the circuit, I found the caps that were only power supply and audio coupling related. Since the circuit is working just fine, I won't touch the caps used into the actual circuits such as PLL oscillator or FM MPX detector for example. Here the updated list, even cheaper at just below 60$.
Wow, that is real vintage. My HP8640B is years ahead of this one. Mine is going up to 520Mhz. I worked for 7 years in a calibration lab. We were doing a lot of RF work. I never seen one of these. We had very nice Marconi 2955 communication test sets and 2305 RF Signal Generators. Great pieces of gear. We were servicing about 2000 different models of test equipments. Real electronic works. Now I'm working mainly with radars.
Bye...
SB
Bye...
SB
I've got two HP8640Bs', 1 I found in a dumpster 
This might be of interest to those following this thread, Software stereo encoder to generate a digital MPX stereo signal for FM radio stations don't know how well this might work for aligning a tuner my sound card ain't good enough.
Regards
James
I also found 5 of these in the same dumpster
This might be of interest to those following this thread, Software stereo encoder to generate a digital MPX stereo signal for FM radio stations don't know how well this might work for aligning a tuner my sound card ain't good enough.
Regards
James
I also found 5 of these in the same dumpster
Attachments
SB
I am really impressed by your thoroughness in overhauling the tuner.
I rebuilt a TU-9900 late last year and I rebuilding a second at the moment. For information I paid £275 for each. About the same price you paid.
I made the changes one by one and listened after each change. So here are my notes.
Last year I changed out all the electrolytic capacitors for 105 degree types. In the power supply I increased the smoothing caps to 4000 uf per rail which probably made the biggest single impact of any change. Changing all the electrolytic caps cleaned up the sound in general. The tone was just right. Changing the power supply caps and increasing the uf per rail firmed the base and cleaned up confusion in the sound.
I tried changing out the tantalum caps. In the end I changed for polyester types. Two sounded better with polystyrene bypasses. ( I can not remember which at present ). Changing these did not make that big a difference but was better than the tantalum.
I changed the ic's for 5532's. This improved the sound stage and added two or three dimensions to the sound. Tone remained unchanged.
I will be interested to see if changing for higher quality ic's makes a bigger difference.
I have not re-tuned either of mine. I think they are reasonably ok. Changing from wide to narrow band shows no change in signal strength or tune frequency so I left the tuning alone.
I am so impressed by your notes - they are so useful to others. I must try to do the same in future. However I hope the above helps.
It is the best receiver I have ever come across. Modifying the audio side makes it equal to any I have heard.
Appreciate your thread.
Don
I am really impressed by your thoroughness in overhauling the tuner.
I rebuilt a TU-9900 late last year and I rebuilding a second at the moment. For information I paid £275 for each. About the same price you paid.
I made the changes one by one and listened after each change. So here are my notes.
Last year I changed out all the electrolytic capacitors for 105 degree types. In the power supply I increased the smoothing caps to 4000 uf per rail which probably made the biggest single impact of any change. Changing all the electrolytic caps cleaned up the sound in general. The tone was just right. Changing the power supply caps and increasing the uf per rail firmed the base and cleaned up confusion in the sound.
I tried changing out the tantalum caps. In the end I changed for polyester types. Two sounded better with polystyrene bypasses. ( I can not remember which at present ). Changing these did not make that big a difference but was better than the tantalum.
I changed the ic's for 5532's. This improved the sound stage and added two or three dimensions to the sound. Tone remained unchanged.
I will be interested to see if changing for higher quality ic's makes a bigger difference.
I have not re-tuned either of mine. I think they are reasonably ok. Changing from wide to narrow band shows no change in signal strength or tune frequency so I left the tuning alone.
I am so impressed by your notes - they are so useful to others. I must try to do the same in future. However I hope the above helps.
It is the best receiver I have ever come across. Modifying the audio side makes it equal to any I have heard.
Appreciate your thread.
Don
Thanks for your comments. It will certainly help me also. I was afraid to increase the supply caps too much. Bigger caps can increase the power transformer current demand, causing other problems. What are the caps that you put to 4000uF, are they the 2 470uF caps (C7,C8)?
I was also concern to change the electrolytic caps used in the actual circuit may affect the circuit adjustments or behavior, in particular PLL and RF circuits.
I will also try to replace the Tantalum caps with ERO MKP1837 caps or Wima MKS-3.
Bye...
I was also concern to change the electrolytic caps used in the actual circuit may affect the circuit adjustments or behavior, in particular PLL and RF circuits.
I will also try to replace the Tantalum caps with ERO MKP1837 caps or Wima MKS-3.
Bye...
Wow tvi , a Brüel & Kjær test set. These are just great test gear. What is this one, an audio analyzer? Were they fuctionnal? I guest, one is just too big to ship to North America :
We were servicing a few of their test equipments. It was just bad that their schematics were so weird and usually in german, if I remember correctly. This is where I learn that capacitor came from the dutch word Kapacitor
, a Brüel & Kjær test set. These are just great test gear. What is this one, an audio analyzer? Were they fuctionnal? I guest, one is just too big to ship to North America :We were servicing a few of their test equipments. It was just bad that their schematics were so weird and usually in german, if I remember correctly. This is where I learn that capacitor came from the dutch word Kapacitor
SB
I changed all the electrolytics in the power supply and audio circuit.
I will check the numbers of the caps tonight on the circuit diagram. However the ones that I increased the value of were the ones from the rails to earth in the power supply. This really cleaned up the base and made it tight. ( previously the base was indistinct and slightly lacking ) I will give yo the numbers tomorrow when I have looked at the circuit.
I made all my changes one by one and listened after each change.
It can take time that way but you do then know the effect of each change.
In the power supply and audio circuit I used electrolytics with greater value in some locations. I used 105 degree caps in all locations. I did not change the rectifier diodes or any capacitors as my tuners sound so good as is. In all I found surprisingly little needed changing and I am really impressed by the end result.
Netlist was also very helpful to me as he had done a similar job earlier.
More info later
Don.
I changed all the electrolytics in the power supply and audio circuit.
I will check the numbers of the caps tonight on the circuit diagram. However the ones that I increased the value of were the ones from the rails to earth in the power supply. This really cleaned up the base and made it tight. ( previously the base was indistinct and slightly lacking ) I will give yo the numbers tomorrow when I have looked at the circuit.
I made all my changes one by one and listened after each change.
It can take time that way but you do then know the effect of each change.
In the power supply and audio circuit I used electrolytics with greater value in some locations. I used 105 degree caps in all locations. I did not change the rectifier diodes or any capacitors as my tuners sound so good as is. In all I found surprisingly little needed changing and I am really impressed by the end result.
Netlist was also very helpful to me as he had done a similar job earlier.
More info later
Don.
Algar_emi
Since you obviously know what you are talking about -not only RF wise- and since I lost that RF generator I have a question on how to get rid of a problem with the tuner.
When listening to silent passages of classical music, I can hear an adjacent station in the background, I'm sure there is a term for this, selectivity I guess. I'd obviously would like to trim that out but since I don’t have a genescope or other RF gear as described in the manual, I'm not very keen to start fiddling with the coils and caps.
What coil should I look for in your opinion? I would mark it and slowly turn it by ear to try to get rid of that interference.
/Hugo
Since you obviously know what you are talking about -not only RF wise- and since I lost that RF generator I have a question on how to get rid of a problem with the tuner.
When listening to silent passages of classical music, I can hear an adjacent station in the background, I'm sure there is a term for this, selectivity I guess. I'd obviously would like to trim that out but since I don’t have a genescope or other RF gear as described in the manual, I'm not very keen to start fiddling with the coils and caps.
What coil should I look for in your opinion? I would mark it and slowly turn it by ear to try to get rid of that interference.
/Hugo
Indeed selectivity. Did you try the Narrow/Wide IF Switch? Try to use the Narrow setting, it may help to prevent this adjacent station from getting through the IF.
The selectivity is coming from the IF. This tuner is using potted LC filter module. This type of modules are usually less selective than the newer ceramic filter but the nice LC filter are often reported as better sounding because they have better phase response. So they cannot be replace with more selective filter, we are stock with them. See the great discussion on http://www.fmtunerinfo.com/#technical, section Gang & Filters. See also a good explaination on filters: http://www.fmtunerinfo.com/filters.html
Quote: "It should be noted that some high-end tuners from the '70s still used the more costly LC IF filters, which were later packaged in sealed block-like enclosures (i.e., no longer had tunable inductors). The reason was most likely that flat group delay, minimum phase filters were not yet available in the ceramic package". These are the type of filters used into the TU-9900
The tuner sensitivity is coming from the front-end with images and spurious rejection as well.
I wouldn't recommend to play with the adjustement without any test equipment. The coils need to be precisely adjusted one after the other.
By the way, there is no real mention in the service manual on how to adjust the fron end. I guest is is not considered field servicable.
The selectivity is coming from the IF. This tuner is using potted LC filter module. This type of modules are usually less selective than the newer ceramic filter but the nice LC filter are often reported as better sounding because they have better phase response. So they cannot be replace with more selective filter, we are stock with them. See the great discussion on http://www.fmtunerinfo.com/#technical, section Gang & Filters. See also a good explaination on filters: http://www.fmtunerinfo.com/filters.html
Quote: "It should be noted that some high-end tuners from the '70s still used the more costly LC IF filters, which were later packaged in sealed block-like enclosures (i.e., no longer had tunable inductors). The reason was most likely that flat group delay, minimum phase filters were not yet available in the ceramic package". These are the type of filters used into the TU-9900
The tuner sensitivity is coming from the front-end with images and spurious rejection as well.
I wouldn't recommend to play with the adjustement without any test equipment. The coils need to be precisely adjusted one after the other.
By the way, there is no real mention in the service manual on how to adjust the fron end. I guest is is not considered field servicable.
I almost completed the tuner upgrade. I'm working on the op-amp OPA2604 upgrade small PCB. The power supply upgrade gave superb result. The supply noise level are now below my DVM threshold (<1mv). I used bigger caps for the two first filtering caps C6,7. I used 3300uF, 35V without any ill effect on the transformer. I'll measure the noise level tonight with my CLIO once the opamp are replaced.
For the rectifier I used UG4D rectifiers. I also replaced the NTE main transistor with the original 2SD313 (The real original were 2SD314 but the 2SD313 has exactly the same specs except for the Vcbo=90 instead of 100V. I used Black Gate caps for the final caps at the output, Panasonic FC at the other locations.
For the rectifier I used UG4D rectifiers. I also replaced the NTE main transistor with the original 2SD313 (The real original were 2SD314 but the 2SD313 has exactly the same specs except for the Vcbo=90 instead of 100V. I used Black Gate caps for the final caps at the output, Panasonic FC at the other locations.
Attachments
Thank you very much for the detailed info. Narrow or wide has no effect. Looking at the manual I noticed quite a few adjustments on the FM pack on page 12. I'd love to find some proper gear to fine tune this beauty.Algar_emi said:
I'm aware of the excellent discussion on the tuner forum, thanks for pointing that out again.
As for your PSU, you seem to have done a nice job. I might try faster diodes one day...
/Hugo
Since you're in Europe, you may try to find Rohde & Schwartz used RF generator. They are also very good. I'll keep you posted on my progress. Example from Germany: http://cgi.ebay.de/Rohde-Schwarz-SM...ryZ31339QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
I just completed the Op-Amp OPA2604 adapter small pcb. It has 2 Wima supply bypass capacitors and four pins sockets. These pins socket are connected between the op-amp output and the Vcc supply. I can connect a resistor there to polarized in Class-A the op-amp. I plan to use it without and without 5K resistors and compare the result.
The small PCB is mounted using an Wire-Wrap IC socket adapter that I cut in two to get both sections of pins on each side of the PCB. The long pins also allows the PCB to be install over the existing parts PCB. The two small round notches on the pcb are to let some room for the new Black-Gate N coupling capacitor that I upgraded on the main PCB.
The two pypass capacitors need a ground connection but there is none on the existing op-amp pins. I will use the pin 1 of IC02, used for frequency compensation on the old IC. On this pin, there is just a capacitor to gnd, C08. I will short this cap to ground with a jumper providing a gnd on pin 1 of the old op-amp IC02.
The small PCB is mounted using an Wire-Wrap IC socket adapter that I cut in two to get both sections of pins on each side of the PCB. The long pins also allows the PCB to be install over the existing parts PCB. The two small round notches on the pcb are to let some room for the new Black-Gate N coupling capacitor that I upgraded on the main PCB.
The two pypass capacitors need a ground connection but there is none on the existing op-amp pins. I will use the pin 1 of IC02, used for frequency compensation on the old IC. On this pin, there is just a capacitor to gnd, C08. I will short this cap to ground with a jumper providing a gnd on pin 1 of the old op-amp IC02.
Attachments
Here the MPX Decoder PCB upgraded with new BG caps and the new OPA2604 dual op-amp.
Finally, the sound. Very good indeed. The upgrade remove any trace of solid state glare. Sound is huge, just listen last night to a CBC live recording event. You could hear the hall, and the voices were just there. Bass are also generous and full. I'm very please with the result.
Very good tuner indeed...
Finally, the sound. Very good indeed. The upgrade remove any trace of solid state glare. Sound is huge, just listen last night to a CBC live recording event. You could hear the hall, and the voices were just there. Bass are also generous and full. I'm very please with the result.
Very good tuner indeed...
Attachments
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