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Old 29th May 2017, 9:24 pm   #81
PJL
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Default Re: HP1715A repair

Before you order the part it would be a good idea to run the symptoms past the hp forum to get confirmation that the chip is indeed faulty.
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Old 29th May 2017, 9:41 pm   #82
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Default Re: HP1715A repair

That is a fair point. I have posted a note to that effect with a summary of symptoms and a link to this forum for the detail.

Regarding Sphere, that comment about a 7% Paypal charge made me cringe. Their website is very cluttered with no search, ordering or payment mechanism which already did not inspire confidence. (Yes I did see the rather quaint hint to use Ctrl-F in the browser). On top of that, the quote containing e-mail I received from them suggested I can pay by sending my address and credit card details (including the security code on the back) via e-mail! They do have a telephone payment option which I will prefer to use, but I will most certainly NOT send my credit card details via the insecure method that is e-mail. As an IT security professional I am actually quite horrified that it was even suggested, but to be fair I am probably more aware (and therefore more sensitive to) than most of the fraud risks involved.

Of course, if I want that rare part, then my options are rather limited and I may have to go to them in the end, otherwise I would have automatically looked elsewhere. Rant over.

Last edited by WaveyDipole; 29th May 2017 at 10:09 pm.
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Old 30th May 2017, 11:10 am   #83
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Default Re: HP1715A repair

I've always thought Sphere's postage charges are steep and take no account of size. Also, if they really surcharge 7% for PayPal, that's excessive. I pay about 4% to PayPal if I sell something on eBay so you can bet that a company is going to be charged less. Maybe some kind person on the HP forum will come up with the goods.

PS: will send the pics of the datasheet pages direct.
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Old 30th May 2017, 1:17 pm   #84
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Default Re: HP1715A repair

Well so far, no one seems to be talking to me on there. Sometimes it takes time so I will give it a week or so to see what happens. In the meantime, thanks for sending me the datasheets direct.
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Old 30th May 2017, 8:06 pm   #85
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Default Re: HP1715A repair

Hi!

Quote:
On top of that, the quote containing e-mail I received from them suggested I can pay by sending my address and credit card details (including the security code on the back) via e-mail! They do have a telephone payment option which I will prefer to use, but I will most certainly NOT send my credit card details via the insecure method that is e-mail. As an IT security professional I am actually quite horrified that it was even suggested, but to be fair I am probably more aware (and therefore more sensitive to) than most of the fraud risks involved.
An organisation based (we hope!) in Canada ought to:-

a) Have had more sense;

b) Have taken the trouble to setup a proper secure electronic payment system besides PP! They are selling a great many rare, and (unobtainium!) spare parts for equipment that stopped being supported by HP and Tek twenty years or more ago, and for the prices they ask for some of these bits you'd have thought they could easily afford to!

However, I have heard mis-giving noises here and there about the internet that Sphere may intend to wind up sooner rather than later, so I wouldn't leave it over long to order the i.c., (even if it means coughing up the extortionate Pay-Pal fee!) if I was you as I can't suggest any other source apart from another 'scope - I don't think QService in Rhodes has got any!

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Last edited by Chris55000; 30th May 2017 at 8:14 pm.
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Old 31st May 2017, 9:27 am   #86
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Default Re: HP1715A repair

Sphere is winding down not up. Walter Shawlee (owner) sometimes posts on the HP_Agilent forum and did say recently that they were getting rid of quite some stock (e.g. 'scope CRTs) to make space. As he gets older he wants to cut back somewhat, but not cease trading.
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Old 31st May 2017, 8:34 pm   #87
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Default Re: HP1715A repair

HI1

Quote:
Sphere is winding down not up. Walter Shawlee (owner) sometimes posts on the HP_Agilent forum and did say recently that they were getting rid of quite some stock (e.g. 'scope CRTs) to make space. As he gets older he wants to cut back somewhat, but not cease trading.
Thanks for clarifying the point!

I think, as a precautionary measure, I'll stay away from oscilloscopes with custom i.cs, hybrids, etc., so I'm not stuck for these things in the future!

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Old 2nd Jun 2017, 3:52 pm   #88
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Default Re: HP1715A repair

I received the FETs kindly supplied by Humber888 in the post this morning.

I have just tested one and this looks promising. The voltages around the FET and Q3 look OK and the voltages around Q2 are close. Voltages around the U1 IC look OK as well.

Q2 E -12.30
Q2 B -11.57
Q2 C -5.02

U1 P2 -0.06
U1 P3 +0.26
U1 P6 -1.16

I examined the sinewave waveform from my valve based sig gen which goes from 100kHz up to 100MHz at the input of A1 it looked OK at all frequencies although the amplitude does start to drop off close to the 100MHz end. This is partly down to the sig gen, but might also be down to the cheap probe I am using.

I haven't heard anything from the Yahoo forum, to any of my questions so have not yet been able to confirm whether the symptoms of the problem with the scope is consistent with a fault A1 chip. There is some activity on the group, but very little so maybe it is just very quiet.
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Old 2nd Jun 2017, 5:10 pm   #89
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Default Re: HP1715A repair

The new FET's look good.

The problem is that a replacement scope is probably going to work out cheaper than getting the replacement part. it is also still not impossible for the fault to lie elsewhere.

I would be tempted to put it aside and setup an ebay search for a 'spares' scope. A 1725A went for £10.50 earlier this month.
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Old 2nd Jun 2017, 5:57 pm   #90
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Default Re: HP1715A repair

I tend to agree (about both FETs and replacement part). I already have a search saved and will check it every now and then. There is one in the USA for about £50, but with shipping that's nearly £150!

Last edited by WaveyDipole; 2nd Jun 2017 at 6:12 pm.
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