This thread is interesting, if a bit old. It also lists the SG2501 as an equivalent...
WTD--Source for LM325H or SG2501 dual voltage regulator IC | Electronics Forums
WTD--Source for LM325H or SG2501 dual voltage regulator IC | Electronics Forums
If you are unable to locate the LM325H if needed, a couple of LM723 's on a perfboard or dead bug might do the trick, cheap. Larry
Easier to retrofit an LM317 and an LM337 (I like them better than 7815 and 7915).
As to the 2N3054 equivalent, look for TIP power devices with the right ratings -- not sure why HP used such HV devices... not needed.
As to the 2N3054 equivalent, look for TIP power devices with the right ratings -- not sure why HP used such HV devices... not needed.
@6L6, Thanks for the link. Didn't have any left from any one. Though a hot pic of a gal in one of the links.
@DDB, Pretty close, but if going that rout not sure if that or the 718/733
combo would be THE scheisse.
@RichEEM, been spending some time on your fine moore pages for
notes and parts and how to build it. I'm with you on that too.
@DDB, Pretty close, but if going that rout not sure if that or the 718/733
combo would be THE scheisse.
@RichEEM, been spending some time on your fine moore pages for
notes and parts and how to build it. I'm with you on that too.
JFET MOd
@DAVADA,
David, when you were having problems with your
HP339a that you were repairing and upgrading
and modding and were concerned that your
wiring was different than the others, could
it have been one of these?
@DAVADA,
David, when you were having problems with your
HP339a that you were repairing and upgrading
and modding and were concerned that your
wiring was different than the others, could
it have been one of these?
@DAVADA,
David, when you were having problems with your
HP339a that you were repairing and upgrading
and modding and were concerned that your
wiring was different than the others, could
it have been one of these?
Yes but there were two devices that HP used here and mine has the other.
They cheeped out here, Could have just used an op amp. This circuit nulls the capacitance of the diodes in the input protection circuit to prevent distortion.
Unless your pointing to the ALC. Hard to see your schematic.
OKay I see. They replaced that with a diode.
David,
Oh, I thought that was the replacement for the diode.
I couldn't figure out why mind didn't have that.
I guess the diode works as well?
Or enough...
Oh, I thought that was the replacement for the diode.
I couldn't figure out why mind didn't have that.
I guess the diode works as well?
Or enough...
A1 Board Mods
Back on the initial HP 339A, The small trim pots for U1, Q2, R50, R51
don't fit, they are too small and can't span the length. It is almost 1/2-inch
and needs a MEDIUM sized trimpot.
I don't really want to splice wires to the small trim leads to make a fit.
Took out most of the compensation, have some stragglers to go.
R27, R28.
Trying to sort out feedback for oscillator, from
Linear Tech AN43. Looking through their oscillator
circuit and the figure 47 or 48 which ever is the correct one.
Will have to wait and do some trips to the part store.
Back on the initial HP 339A, The small trim pots for U1, Q2, R50, R51
don't fit, they are too small and can't span the length. It is almost 1/2-inch
and needs a MEDIUM sized trimpot.
I don't really want to splice wires to the small trim leads to make a fit.
Took out most of the compensation, have some stragglers to go.
R27, R28.
Trying to sort out feedback for oscillator, from
Linear Tech AN43. Looking through their oscillator
circuit and the figure 47 or 48 which ever is the correct one.
Will have to wait and do some trips to the part store.
A1 Board: Optimizing the LME49740
Then, while its chassis is open
trying to figure out how to optimize
this quad op amp that I put in the HP 339a.
Now that I've upgraded it. I'm not sure how
to find the operating points of the original
and what, how to change the circuit component
values for the replacement LME49740 for
U2C - Summing Amp
U2B - Integrator
U2A - Difference Amp.
When I get to U3 - Buffer Amp, I have the
OPA134. I'm not sure what the original
U3 is driven at and how I would adjust
OPA134 for the same output.
From what I gathered from the
datasheet I'd use negative feedback with 1Kohm
and put 10 ohms between pin2 and pin3 the
- pin and + pin inputs.
I'll also have the same question as I go
through each board. I know some of the
work has been done by you guys over in
the long thread, wondering how I apply it
with these devices?
Trying to understand this as I go through it now.
Then, while its chassis is open
trying to figure out how to optimize
this quad op amp that I put in the HP 339a.
Now that I've upgraded it. I'm not sure how
to find the operating points of the original
and what, how to change the circuit component
values for the replacement LME49740 for
U2C - Summing Amp
U2B - Integrator
U2A - Difference Amp.
When I get to U3 - Buffer Amp, I have the
OPA134. I'm not sure what the original
U3 is driven at and how I would adjust
OPA134 for the same output.
From what I gathered from the
datasheet I'd use negative feedback with 1Kohm
and put 10 ohms between pin2 and pin3 the
- pin and + pin inputs.
I'll also have the same question as I go
through each board. I know some of the
work has been done by you guys over in
the long thread, wondering how I apply it
with these devices?
Trying to understand this as I go through it now.
Oscillator link:
http://cds.linear.com/docs/en/demo-board-schematic/DC1858A2-SCH.pdf
Oh I see there is difference feedback between LT1468 in A1U1 positive,
and in the above schematic. They use their same opamp in the buffer
LT1468, but I wonder why it doesn't work so well here in the
HP339A? So on with the OPA134 for the A1U3 buffer.
http://cds.linear.com/docs/en/demo-board-schematic/DC1858A2-SCH.pdf
Oh I see there is difference feedback between LT1468 in A1U1 positive,
and in the above schematic. They use their same opamp in the buffer
LT1468, but I wonder why it doesn't work so well here in the
HP339A? So on with the OPA134 for the A1U3 buffer.
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@richEEM, I don't know that the 5V is used in here, might go to something not shown.
It does go to something else not shown.
Its in the if you search Linear Teachs site, look for DC1858A
The use is interesting, it's for testing ADCs...that is what the 5V and 12V suppliers are for.
on the MOLex conn.
It does go to something else not shown.
Its in the if you search Linear Teachs site, look for DC1858A
The use is interesting, it's for testing ADCs...that is what the 5V and 12V suppliers are for.
on the MOLex conn.
Last edited:
Update, A1U1 installed adjustment pots, I thought correctly,
but then I had about 64 volts on the A1TP1 and GND. 🙁
Explains why the QA400 was clipping.
I'm also wondering if one of the compensation caps or
resistors needs to remain.
Probably should turn down the amplitude adjust before
plugging in anything again.
Not sure if little A1U1 opamp is now toast. last I looked
it was about .19v w/some distorted wave form and then
baby started puking so haven't gotten back at it yet.
Pics at 11.
but then I had about 64 volts on the A1TP1 and GND. 🙁
Explains why the QA400 was clipping.
I'm also wondering if one of the compensation caps or
resistors needs to remain.
Probably should turn down the amplitude adjust before
plugging in anything again.
Not sure if little A1U1 opamp is now toast. last I looked
it was about .19v w/some distorted wave form and then
baby started puking so haven't gotten back at it yet.
Pics at 11.
64 volts must be a typo? What is it really?
Which opamp did you use for A1U1? If the LT1468, you shouldn't need any comp cap, but may need a 100 ohm resistor between the opamp output pin and the rest of the circuitry. David might know better.
Which opamp did you use for A1U1? If the LT1468, you shouldn't need any comp cap, but may need a 100 ohm resistor between the opamp output pin and the rest of the circuitry. David might know better.
@richEEM, No typo. I was like WTF (What The Fudge), and that is from my calibrated Fluke Scopemeter. Now that I'm thinking about it, that might be measured +peak to -peak. But still that is a problem, as it would be 32V.
That makes sense that above about .01V on the Oscillator output dial
it would clip the QA400.
I managed to start the calibration procedure and found when it came to
adjusting the A1U1 and the R30 level, to dial in a -.4V reading, the initial
reading before dialing it in measured +2.3V. I'd say just running it a bit
hot. I finished up dialing it to -403.1 mV
@David, close to 100 ohm on 6. I want to test it ground ghrough.
ok to be continyed. Film procs are on strike, mahbe
That makes sense that above about .01V on the Oscillator output dial
it would clip the QA400.
I managed to start the calibration procedure and found when it came to
adjusting the A1U1 and the R30 level, to dial in a -.4V reading, the initial
reading before dialing it in measured +2.3V. I'd say just running it a bit
hot. I finished up dialing it to -403.1 mV
@David, close to 100 ohm on 6. I want to test it ground ghrough.
ok to be continyed. Film procs are on strike, mahbe
That voltage figure is not possible -- the supplies in your 339 would give you only 30Vp-p at the highest level, which isn't even possible. Look at the schematic and rethink what you see or better, remeasure.
Couldn't capture the screen. I think I'd connected to the GND lug
over on the P/S board. There is a gremlin in there somewhere as
it seems to act up from time to time.
Can we double up a power supply to double its voltage?
We got +15, -15 on one side and +15, -15 on the other,
can they somehow get superimposed on each other
for 60 VDC?
Or what if signal is feeding through the output regulator making
it sense a different voltage than it really is..and it starts cranking out more
voltage than supposed to?
How do we explain input clipping on the QA400 at
.1 V oscillator output?
I don't have answers, just observations.
However, I did discover the center wiper to the Oscillator Level
Pot (adjusts through the Frequency Venier) that I had replaced broke off.
I put a 100 ohm resistor across the cut trace at pin 6.
Working through cal procedure as best as I can.
It's more civilized now, but harmonics are BIG.
Almost have pics at 11 maybe tomorrow.
over on the P/S board. There is a gremlin in there somewhere as
it seems to act up from time to time.
Can we double up a power supply to double its voltage?
We got +15, -15 on one side and +15, -15 on the other,
can they somehow get superimposed on each other
for 60 VDC?
Or what if signal is feeding through the output regulator making
it sense a different voltage than it really is..and it starts cranking out more
voltage than supposed to?
How do we explain input clipping on the QA400 at
.1 V oscillator output?
I don't have answers, just observations.
However, I did discover the center wiper to the Oscillator Level
Pot (adjusts through the Frequency Venier) that I had replaced broke off.
I put a 100 ohm resistor across the cut trace at pin 6.
Working through cal procedure as best as I can.
It's more civilized now, but harmonics are BIG.
Almost have pics at 11 maybe tomorrow.
I had some general questions about the Calibration Procecure (Cal Procs)
I don't have the HP3571A nor the HP3044A. QA400, ScopeMeter, Scope,
multi meters.
5-17 Notch Filter Null Adjust.
Step o. onward.
5-18 High Frequency Adjustment
Step d. onward.
General Question,
after placing the LT1468 in A1U1 and
LME49740 in A1U2A, U2B, U2Cs,
I'm not sure how to adjust those sections
for the new opamps.
I don't have the HP3571A nor the HP3044A. QA400, ScopeMeter, Scope,
multi meters.
5-17 Notch Filter Null Adjust.
Step o. onward.
5-18 High Frequency Adjustment
Step d. onward.
General Question,
after placing the LT1468 in A1U1 and
LME49740 in A1U2A, U2B, U2Cs,
I'm not sure how to adjust those sections
for the new opamps.