Dany,
I hope you have some good 7199 tubes. They are scarce/expensive, I might have one if you need it.
The EZ81 is a 9-pin tube and doesn't have the current capacity of the GZ34/5AR4. As well, the EZ81 is a 6 volt tube and the power trans of the AA-100 is marginally rated. I have an ancient Mullard GZ34 chugging away in my Tubelab SPP. They seem to last forever. Solid state rectification will raise the B+ quite a bit so you might have to put more resistance in the filter string. I put a Hammond filter choke and another cap before the stock Heath filter string on my amp. One thing that Heath goofed on was a 60uF cap connected to the GZ34. Most say that 50uF is the max recommended as the first cap.
Cheers, S.
I hope you have some good 7199 tubes. They are scarce/expensive, I might have one if you need it.
The EZ81 is a 9-pin tube and doesn't have the current capacity of the GZ34/5AR4. As well, the EZ81 is a 6 volt tube and the power trans of the AA-100 is marginally rated. I have an ancient Mullard GZ34 chugging away in my Tubelab SPP. They seem to last forever. Solid state rectification will raise the B+ quite a bit so you might have to put more resistance in the filter string. I put a Hammond filter choke and another cap before the stock Heath filter string on my amp. One thing that Heath goofed on was a 60uF cap connected to the GZ34. Most say that 50uF is the max recommended as the first cap.
Cheers, S.
Final word about this HG88 = the 1st of the HG series. Geoff Kremer from Maritron Technical Services UK(who emaikled me the schematic herein) advised me that indeed the caps into the grids of the ECC83 pre the ECL82's are indeed 1000Pf, but I can increase their value to 5000Pf - which I did. The HG88 also came w/ a kit of spares. I added some parts that were missing, but not the 4 3/8" Panel Fixing Nuts. Only 4 Miniature co-axial Iput plugs.
About the Heathkit AA-100. I've already tested all the tubes w/ the AVO VCM3 & they're all OK. The 7199's match favorable.
A GZ34 has indeed more o/p(200mA) than an EZ81(150mA). The GZ34 tests fine - probably have few on hand. I also have lots of 5AR4 = North American equivalent - just in case.
Dany, Toronto
About the Heathkit AA-100. I've already tested all the tubes w/ the AVO VCM3 & they're all OK. The 7199's match favorable.
A GZ34 has indeed more o/p(200mA) than an EZ81(150mA). The GZ34 tests fine - probably have few on hand. I also have lots of 5AR4 = North American equivalent - just in case.
Dany, Toronto
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Hi DanyF from the UK.
Can I just tell you that over here the Black 'Hunts' Mould seal caps (in your pre amp section) have a ''Change on sight'' warning. They become electrically leaky and are better resistors than caps.
Likewise the yellow TCC coupling caps in the power amp section are not much better. I would replace all of them... but C18, C19 and C20 to preserve the ECL82s.
At least make sure they are not putting positive volts on the pin 3 grids of the ECL82s. They will have a short life if they have.
Alan
Can I just tell you that over here the Black 'Hunts' Mould seal caps (in your pre amp section) have a ''Change on sight'' warning. They become electrically leaky and are better resistors than caps.
Likewise the yellow TCC coupling caps in the power amp section are not much better. I would replace all of them... but C18, C19 and C20 to preserve the ECL82s.
At least make sure they are not putting positive volts on the pin 3 grids of the ECL82s. They will have a short life if they have.
Alan
Hi Alan
To coret you - I'm not in the UK. I'm actualy located in Toronto Canada!
Now, the low voltage Lytics were @ fault - I canged them all w/ higher uF values per Geoff's advice. The Hi volt Lytics weren't shorting, just dried out of their inside chemicals = a common cause. That's why I connected new ones(w/ a bit higher uFs) accross them = no more hum = common practice, again.
The Grid caps in the ECC63 - I installed new onse w/ 5,000 pF instead of the 1,000 - again w/ the rcomandation of Geoff. In the process I also replaced the coupling capsfor the ECL82's w/ same capacitance - made w/ 2 in series in order to achive a higher voltage rating(I think 2 w/ 160v = 320v.
Dany
To coret you - I'm not in the UK. I'm actualy located in Toronto Canada!
Now, the low voltage Lytics were @ fault - I canged them all w/ higher uF values per Geoff's advice. The Hi volt Lytics weren't shorting, just dried out of their inside chemicals = a common cause. That's why I connected new ones(w/ a bit higher uFs) accross them = no more hum = common practice, again.
The Grid caps in the ECC63 - I installed new onse w/ 5,000 pF instead of the 1,000 - again w/ the rcomandation of Geoff. In the process I also replaced the coupling capsfor the ECL82's w/ same capacitance - made w/ 2 in series in order to achive a higher voltage rating(I think 2 w/ 160v = 320v.
Dany
Hi DanyF,
Thanks, I fully understood you are in Canada, the greeting was from the UK, where I am based.
We have a lot of experience, here in the UK, with the Hunts 'Black' caps and the TCC 'yellow' caps. They are notoriously unreliable and I was just pointing you in a direction to at least check them.
And I'm confused, you say the ECL82 coupling caps (C18/C19/C20) have been replaced? But your completed pictures still shows the originals?
Best, Alan
Thanks, I fully understood you are in Canada, the greeting was from the UK, where I am based.
We have a lot of experience, here in the UK, with the Hunts 'Black' caps and the TCC 'yellow' caps. They are notoriously unreliable and I was just pointing you in a direction to at least check them.
And I'm confused, you say the ECL82 coupling caps (C18/C19/C20) have been replaced? But your completed pictures still shows the originals?
Best, Alan
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Hi Alan
I'm sorry about being late answering you, but both of us = I & my wife have been busy planting veggies in the garden & in big & huge pots located on our huge(42') veranda in the back of the house. Even earlier today I've been planting - forced to stop due to the rain. Previously, I'd to till the soil in the garden. still have to plant & place seeds in the garden. &, lots of different cherry(black & red, yellow, orange, red) tomatoes plants have finally bore tiny plants. Also other big ones. I'm currently waiting to seedlings of extremely hot peppers.
Now, about C 18/19/20. I never said I'd replaced them - I think you're referring to the yellow caps. These don't leak & the appropriate voltages attest to that. However, I did replace the o/p caps of the ECC83 - just as much as the i/p ones = blue. Again, all the voltages match very closely for the 2 channels.
Regards, Dany & Judith
I'm sorry about being late answering you, but both of us = I & my wife have been busy planting veggies in the garden & in big & huge pots located on our huge(42') veranda in the back of the house. Even earlier today I've been planting - forced to stop due to the rain. Previously, I'd to till the soil in the garden. still have to plant & place seeds in the garden. &, lots of different cherry(black & red, yellow, orange, red) tomatoes plants have finally bore tiny plants. Also other big ones. I'm currently waiting to seedlings of extremely hot peppers.
Now, about C 18/19/20. I never said I'd replaced them - I think you're referring to the yellow caps. These don't leak & the appropriate voltages attest to that. However, I did replace the o/p caps of the ECC83 - just as much as the i/p ones = blue. Again, all the voltages match very closely for the 2 channels.
Regards, Dany & Judith